Gruyere, Mushroom, & Caramelized Onion Bites
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Caramelized onion bites with sautéed crimini mushrooms, balsamic caramelized onions, and applewood smoked gruyere cheese. Thee perfect little appetizers! They’re made with puff pastry and take no time at all to whip up! These are the perfect appetizers to serve your guests this holiday season.
Boom! Flakey puff pastry topped with balsamic caramelized onions, sauteéd mushrooms, a hint of garlic, and a smoked gruyere cheese bomb mixed right in. <– Dis is my life. Me likey likey. Be it a caramelized onion tart/tartlette, puff pastry bite, or a caramelized onion panini melt, I am down for it all.
These caramelized onion bites are a game-changer for me. They’re perfect to serve to guests before a big holiday dinner. Also, they totally look fancy shmancy but no body really needs to know that the caramelized onion and sauteéd mushroom filling can be made up to 48 hours ahead of time. Snappy. Snappetizers. Has that term been coined already? Because i’m coining it if it hasn’t. Appetizers in a snap. That’s some of my best thinking before my 9am cup of coffee *pat on the back* (and it’s well deserved).
I’ve been wanting to get these puff pastry bites for A. LONG. TIME. They’re perfect for holiday parties and they look oh so, elegant. So elegant that you have the guests fooled on how long it actually took to make these bad boys. When you’ve got a holiday part going on, the last thing you want to do is spend too much time on any one dish. Not gonna do it. You’ve gotta simplify and do some do-ahead work. And these caramelized onion bites fit right into that agenda.
Let’s talk about the recipe. I’m using 2 medium yellow onions and about 5-6 ounces of crimini mushrooms. A little sugar, a little balsamic vinegar, and a 1/4 teaspoon of thyme.
We’re going to start by sautéing the mushrooms in a few tablespoons of oil for 4-5 minutes. Once they start to brown, remove them to a bowl. Add the remaining butter and the onions. Let them hangout in the pan for 5 minutes. Remember to use a cast iron or stainless steel skillet. You want to avoid using a nonstick skillet as the onions won’t caramelize as well. After the 5 minutes, toss in the sugar and thyme. Now crank the heat down to about medium-low and cook for a total of 25 minutes and keep checking on them every 5 minutes or so to make sure they aren’t caramelizing to fast. Add the balsamic to help deglaze the pan and when it’s all been soaked up, you’re done. Add the onions to the mushrooms and season with a little garlic powder + salt and pepper.
Let your filling come to room temperature, you can store it in an air tight container for up to 48 hours in the refrigerator. If you decide to make the filling ahead of time, zap it in the microwave to bring it back to room temp before continuing with the recipe instructions. Mix in the gruyere cheese and combine well.
Remember to thaw your puff pastry in the refrigerator overnight. This will ensure that you don’t get any cracks trying to pry open the puff pastry sheets. Cut the puff pastry sheet into small squares or rectangles. I cut mine into 2-inch squares. Brush them with a beaten egg using a pastry brush. Drop about a tablespoon of caramelized onion mixture on each puff pastry square.
Bake them for 20-25 minutes and make sure to rotate the pan halfway though for even baking. Top with chopped parsley and serve warm. In the word’s of Ina Garten, how easy is that?
Look at each of those puff pastry layers and how perfectly they separate from each other. It’s like taking a bite out of 10 potato chips at the same time, only less crunchy, and more buttery. Okay, so not like a potato chip at all, really.
Caramelized onion bites are going to make your holidays more amazing. The garlic, the mushrooms, the caramelized onions, and smoky gruyere. <– that’s the stuff dreams are made of!
Gruyere, Mushroom, & Caramelized Onion Bites
Caramelized onion bites with sautéed crimini mushrooms, balsamic caramelized onions, and applewood smoked gruyere cheese. Thee perfect little appetizers! They're made with puff pastry and take no time at all to whip up! These are the perfect appetizers to serve your guests this holiday season.
Ingredients
- 4 tablespoons salted butter, divided
- 2 tablespoons vegetable oil, divided
- 5-6 ounces crimini or button mushrooms, sliced
- 2 medium yellow onions, thinly sliced
- 1/4 teaspoon dried thyme
- 1 tablespoon sugar
- 1 1/2 tablespoon balsamic vinegar
- 1/4 teaspoon garlic powder
- salt and pepper, to taste
- 4 ounces grated gruyere cheese (I used applewood smoked gruyere)
- 1 package (1 pound) frozen puff pastry, thawed
- 1 egg, lightly beaten
Instructions
- In a large cast iron skillet over medium heat, heat 1 tablespoon of oil along with 1 tablespoon of butter. Add the mushrooms and sauté for about 5 minutes until tender. Remove and set aside in a medium bowl.
- Heat the remaining 3 tablespoons of butter along with the 1 tablespoon of oil and sauté the onions for 5 minutes. Add the dried thyme and sugar and continue to cook for 25 minutes on medium low heat. Make sure to stir the mixture every 5 minutes or so. If the onions are caramelizing too fast, turn down the heat a little more. Add the balsamic vinegar to deglaze the pan, allow the onions to soak it all in. Turn off heat. Add the onions to the mushroom mixture. Season with the garlic powder and salt and pepper to taste, stir to combine. Allow to cool to room temperature. Mixture can be kept in an air-tight container and refrigerated for up to 48 hours at this point. Allow to come to room temperature before proceeding. Add the gruyere cheese and mix well.
- Position two racks in the upper and lower thirds of the oven. Preheat the oven to 400 degrees F. Line 2 baking sheets with parchment paper or silicone mats.
- Using a knife or a pizza cutter, cut the puff pastry into 2-inch squares and place them on a lined baking sheet. Make sure the puff pastry is cold before proceeding. If not, allow it to rest in the refrigerator for 10-15 minutes before proceeding. Using a pastry brush, brush the beaten egg on the squares. Place a tablespoon of caramelized onion mixture in the center. Bake for 20-25 minutes, rotating the pan halfway in between until crisp and golden brown. Let cool slightly before serving.
Notes
- Make sure the puff pastry is cold when it goes into the oven. If at any point it becomes soft, allow it to rest in the refrigerator for 15-20 minutes or until it firms up again. Do not open the oven door during the first 10 minutes of baking time. Frequently opening the oven may cause the puff pastry to not 'puff up'.
- Mozzarella or gouda cheese may be used to replace the gruyere. I really like the smoky flavor of applewood smoked gruyere with these bites.
- If you've prepared the caramelized onion mixture ahead of time, you can zap it in the microwave for 30 seconds to bring it back to room temperature quickly.
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99 Comments on “Gruyere, Mushroom, & Caramelized Onion Bites”
I make a tart just like this . . but love your idea of pre-cutting the puff pastry. . so beautiful and yes, a great appetizer for the holidays!
I tried making this recipe and followed the instructions on the store bought puff pastry box to the T but the puff pastry was too puffy! Do I need to roll it out a bit? What did I do wrong?
Hi Winnie, for next time, i’d suggest scoring a ¼ inch border on the puff pastry (and place the onion mushroom mixture inside the borders) this should keep the pastry from puffing up too much. You could even use a fork and just pierce holes all over the unbaked puff pastry squares before adding the pastry on top and baking. Either method would work. It’s really nothing you did, the brand of puff pastry you used just happened to be extra puffy 🙂
Ok–I tried to make this for a holiday party and they didn’t puff and were so tiny. Any idea what happened?
Hi Heather,
Hmmm. Did you perhaps open the oven door during the first 10 minutes of baking time? Sometimes, the puff pastry doesn’t rise if the oven temperature falls too much before the puff pastry has a chance to start puffing up. It could also be that the puff pastry wasn’t cold enough when it went into the oven. If the kitchen is super warm or if you live in a warm climate, the puff pastry sheets sometimes need a few minutes in the refrigerator before going into the oven. I’ll also add these as notes into the recipe, thanks for your feedback.
Greetings Marzia, Great recipe. I’m doing this for our Christmas gathering. I noticed the pictures included a green well sliced leaf. Is that parsley?
Hi Paul! Yes, that’s parsley. 🙂 Just sprinkled some on to make it look a little more attractive for pictures!
I made a double batch of these last night for a party. They were wonderful and a big hit! There were a handful left over and I heated them on low in the oven and topped them with basic scrambled eggs with cheese and tomatoes. Also delicious!
Maybe I’m missing it but when do you add garlic powder and salt and pepper?
Sara, you add the garlic powder, salt, and pepper after you combine the caramelized onions and mushrooms in a bowl.
hi,just did it today….I mixed the mushrooms with emmenthal cheese . They were ok but the cheese was in a way like overcooked before the pastries puffed properly..so i had to add little bit of cheese as a topping and left it few seconds to melt
The recipe specifically calls for gruyere, and although emmental cheese is similar, it’s always best to use the ingredients i’ve tested the recipe with. If you change the ingredients or quantities, it changes the recipe. Emmenthal cheese contains less fat than gruyere, perhaps this is why the ingredient didn’t work as a good substitute.
Made these for Valentine’s Day. Used a heart cookie cutter for the pasty dough and they turned out perfectly! This recipe is a winner for sure!
Wish I could share a picture, so happy with how this turned out.
Great idea! I am making these for Christmas and will try using a large star cookie cutter!
Thanks so much for the recipe!
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These were great. However, having made these and french onion soup numerous times, you underestimate the time to properly caramelize onions. That creamy deep brown (but not burnt) texture takes at least twice what you listed (mine took an hour in a large cast iron). Not a deal-breaker, but certainly not a quick appetizer.
I made these on Saturday night for a small dinner party and they were a tremendous hit! Followed your recipe exactly but use the mission fig balsamic vinegar instead of regular balsamic; so delicious!
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I have made these a couple times now. Always a big hit. I have made them with and without mushrooms. I cut the puff pastry into 16 equal squares. I do not add any garlic, balsamic vinegar or sugar. Just onions cooked down in the oil/butter/salt topped with gruyere. They cook perfectly every time and are simple, elegant and delicious. You really only need 3 ingredients which is amazing!!
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So did I miss something or when do you add the cheese? I can’t wait to try this recipe for aChristmas party we are attending this coming weekend and I’m getting my shopping list made out. Just re-read and I still missed the chees step??!!! Thanks for your input!!!
At the very bottom, in step #2 🙂
Delicious! People at the party I went to loved these! I thought I had the right cheese on hand, but I had Gouda, and they turned out wonderful!
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Can this recipe be made ahead of time and then frozen?
I’ve never tried freezing it so I really couldn’t say!
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Really wonderful recipe! I took this to Christmas dinner after a friend gave me a bag of wild mushrooms. Just lovely. This dish travels well because you can keep the mushroom mixture separate from the puff pastry and then assemble and heat them for just a few minutes before serving. I may try this with sherry sometime too.
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I’ve made these at least three times in the last 2 months they are sooooo good! Simple easy too and they are so impressive. My puff pastry didn’t really fully puff in the past (still tasty) but this time I had been using the oven before I put them in, 425 roasting potatoes, and they are significantly more “puffed.” I
did turn down to 400 before putting them in, but the hot oven made a difference. I also didn’t have parchment and used foil, rubbed butter all over it. Worked great. Thank you for the great recipe!!!
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I made these for a baby shower and they were so good, I am making again for the baby’s first birthday and some to bring along next weekend with friends. you wont be disappointed!
Amazing recipe,
Easy to make
Taste Great
I made these for a Christmas party and they were excellent, everyone loved them.
Versatile and delicious!
Made this and everyone loved it. Will make it again.
Hi Marzia, can i make these one day ahead?
I’ve made the filling a day ahead and then assembled the day of and that’s worked out fine. As far as assembling and baking ahead of time goes, for best results I suggest preparing the day of. I find the puff pastry looses a bit of it’s magic when you reheat it.
HI Marzia,
I was wondering what you think of how this appetizer travels? I notice one comment below that says it travels well. I was actually planning on making everything and traveling to a friends with it (about 30 minutes away). Does it serve well at room temperature or should it be warm? If I don’t get to make this recipe for my friend’s party, I’ll definitely make it at home. thanks!
Yes, you can serve this at room temperature if you’d like. I personally prefer them a little warm so I suggest reheating them in a 300ºF oven for 10-15 minutes before serving. If you’re making these before traveling with them I suggest making them ahead of time so that they have a chance to cool before you cover/transport them. If you cover them right out of the oven the puff pastry may lose some of that beloved crispness. Hope everyone at the party enjoys them! 🙂
Can this be made with phyllo instead of puff pastry?
Unfortunately phyllo is not a good substitute for the puff pastry.
Omgosh these are sooo good! I used mozzarella and queso fresco cheese. Keeping this recipe thanks for sharing!1
These are delicious!!! I wanted to make them ahead of time so I made the filling and cooled it to room temperature as you suggest. I rolled out the thawed puff pastry slightly to 12×12 inches and cut it into 24 pieces. I fit each piece of pastry into a mini muffin pan to make mini crusts and placed the filling to the top of each cup, I then covered the pans with plastic wrap and then foil and froze them overnight. I just popped them out the next day and into a freezer bag for later use. When ready to bake I simply place the frozen cups back into the mini muffin pans and bake for 20 minutes at 400 degrees.
I’ve made these twice now and they’re so good. I’m always looking for party food to make ahead, and these tarts are perfect.
Can I add a little apple or pear?
Sure! I do suggest cooking the pears or apples to draw out that moisture before using them in the filling, though.
Absolutely delicious. I made this recipe today and took it to a dinner and it was a huge hit. Everyone loved it and wanted the recipe. The only thing I changed was that I used fresh garlic instead of powder. Fabulous, honestly
How far in advance can I assemble and put in fridge . Want to do this ahead of time so I can just put in oven when guests arrive?
The filling can be prepared a day in advance. I haven’t tried assembling these ahead of time and baking later, but my best guess is it would be okay to do about 2-3 hours ahead.
Mel, I have been making these for years now and I completely assemble them and IQF them on parchment paper covered cookie sheets. I then store them in layers on parchment in a 15”x10”x2” plastic food service container. I can get 4 layers in a container. I pull a layer out at a time and bake it on the same parchment and no need to defrost. I serve these at Thanksgiving and Christmas and any other fancy party we might have. Always a huge hit and all the work is done way in advance. Using the parchment also means no pan to wash after! I usually double this to have as much on hand as possible. I have a second freezer, so that really helps. They keep more than 3 months. I have also had extra filling and frozen that too. I am not a balsamic vinegar fan so I substitute Sherry Vinegar and use half the amount of sugar since I use sweet onions. Cheers!
Exceptional! My “go to” appetizer. Everyone loves them.
I am planning on making these for a 4th of July party and am thinking about using a star cookie cutter. Do you think that will work? Of course I would score them along the perimeter.
That sounds like a fun idea! Hmm. I think the star shape could work, I’m just worried about the tips of the star and if they’d burn in the amount of time it takes for the puff pastry to cook all the way through. I suggest doing one test pastry and see how it works out 🙂
Marzia, I took your advice and did a test using a star cookie cutter for the 4th of July. The first star (about 3″) was too big in that the pastry to filling wasn’t right (too much pastry). I then tested a star that was about 2 1/4″. It worked perfectly and the star bites were a big hit! I was sure to score inside the stars and put the filling in the middle. Thanks for a great recipe!
Excellent! Glad it worked out. Thanks for reporting back as I’m sure others may be interested in using a different shape as well! 🙂
I can only find hickory smoked gruyere and regular. No applewood smoked. Which should I use, Hickory smoked or regular? thanks
Either would work! Totally your call!
I made this as a pizza. I used store bought pizza dough. I baked the dough for about 10 minutes before I added the mushroom mixture. I then put olive oil and fresh garlic on the crust topped with the mushroom mixture and baked for 20 minutes. It was delish.
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Filling is SO GOOD but even following the directions exactly, the puff pastry was too much carb and super puffy – the topping got lost in it! I made it again an filled mini phyllo dough cups and they were perfect for us. Also very good on simple crostini or a cracker.
This recipe is soooo good. The taste the texture is perfect. Some of my friends like only cream cheese so I switched and add 1/2 tsp of cream cheese at base and the rest of the filling on top. They loved li!!!!i think this is such a perfect recipe that it simply adapts .
I made these for Thanksgiving this year, this recipe was a big hit with everyone. I got compliments from all of my guests. This recipe will be a Thanksgiving tradition from now on.
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Has anyone tried crescent roll dough rather than puff pastry?
Where can you buy crescent dough?
Elizabeth-crescent rolls are in the refrigerator section of the grocery store by the rolls of biscuits.
Can I freeze the mixture ahead of time? Or will it stay in the fridge for 3 days?
It’ll be fine in the fridge for 3 days!
Made these last night for a NYE party. They were tasty, even though I forgot the garlic powder and balsamic (doh!). Like another commenter, though, they were rather too “puffy — the edges did not rise up around the filling like in the pics, and it felt like they should have more filling in them. Should I maybe score the dough? Puff pastry is the bomb but can be a little tricky. Thanks for the delicious recipe, I will add this to my repetoire!
Just a thought: You might have dragged the knife blade through the puff pastry dough. If you cut straight down the edges won’t be sealed and it will allow the dough to puff up better.
Made this recipe for a party tonight. I actually added shaved ribeye on one side of pastry raw with steak seasoning on it. Cooked perfectly! I’m not sure if they’ll make it there because we keep eating them. Are there any suggestions of a dip I could serve with them?
Let me start off by saying, I’m a horrible cook. That being said, these tarts are so easy to make, the instructions really make the prep process so much easier.
I have made these tarts at least 4 times and, by popular demand, I am making them for another party tomorrow night. I would encourage everyone out there to make them at least once. 5 stars!!
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Has anyone tried making these in the mini pastry shells? I have a jar of bacon jam that I love and was thinking a little of that in the shell with the onion mushroom mixture on top and topped with the parmesan. What do you think?
Bacon Jam…. what is that? It sounds wonderful.
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I made this for neighbor couple. Most impressive thing I ever made and so delicious.
What can I substitute the balsamic vinegar with ?
these sound so good. I’m curious though if they could be made up to the point just before baking and frozen, to be baked at a later date! I’m in an appie exchange and this would be awesome!
Can these be frozen, then reheated for serving?
I made the first batch with non frozen puff pastry and they came out great. The second batch I made with the frozen pastry and they puffed up so much they pushed the mushrooms off. Still delicious. Great and easy.
I made these two years ago for Christmas and my family still talks about them. They’re such a good idea and super tasty!
Thank you for such an amazing recipe! Many asked about making this in advance so im posting this maybe it’ll help someone. I have made this many time. If it’s to be consumed immediately i’ll follow the exact recipe to the t. If i need to make them in advance for any party, here’s what i did: instead of slicing, i chop both onion and mushroom, recipe stays the same. After cooking i spread them on puff pastry sheet and roll them tightly, wrap in sling wrap and into freezer. When ready to bake, take them out & let them sit at room temperature until just soft enough to cut. Bash outside with egg wash and cut into 1 inches pinwheels. Bake at 400 until cook. Optional: take them out at the last 5 minutes and sprinkle with shredded mozzarella . These reheat really well too (350 for 10 mins)
A winning favourite every time I make them!
Sensational!
This recipe was so unique & tasty. I made more than 20 pieces for just 4 guests & it was all gone.
Yummy & looks tantalising, trying recipe tonight . Thanks for sharing recipe.
Awesome recipe, thanks.
I’m planning to make this recipe and wondering if I need to roll out the puff pastry sheet?