Gruyere, Mushroom, & Caramelized Onion Bites
This post may contain affiliate links. Please check our privacy and disclosure policy.
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.
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.
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!
- 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
- 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.
- 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.
We are a participant in both the RewardStyle and Amazon Services LLC Associates Program, which are affiliate advertising programs designed to provide a means for sites to earn advertising fees by advertising and linking to amazon.com and through RewardStyle.