Caramelized Onion Spinach Feta Savory French Toast Casserole
A caramelized onion, spinach, and feta breakfast casserole. This savory french toast casserole is easy to make ahead and pop it in the fridge. It’s great to serve for brunch but also yummy with a side salad for dinner!
So clearly, i’m on some kind of crazy caramelized onion train and not willing to get off. Yes friends, it’s true! But it’s bold flavors like these that make the holiday gatherings a little more cozy, a little more fun, and a LOT more delicious.
I’m calling this a ‘savory french toast’ but you can call it a ‘breakfast casserole’ if you wish, or we can drop both names and just call it what it really is — ‘the best brunch ever’. We’re talking layers of diced french bread, caramelized onions, garlic sautéed spinach, and shredded gruyere + provolone all drizzled with a feta egg mixture. This is perfect to make ahead for Christmas brunch. Prep and have everything ready to go the night before, pop it in the fridge and bake it off fresh in the morning.
You are going to love these flavors.
I was a little hesitant to name this a ‘savory french toast’ mainly because I had never seen or heard of one before. Have you? It’s really more of a strata but really, what matters most is that it’s A BREAKFAST CASSEROLE.
And also, because it kinda is a breakfast casserole, but it’s kinda not. But one quick search on Google, and french toast of the savory variety actually do exist. WHAT? Where have you been all my life? I’m trying them all. And let’s be real here, anything with cheese is > anything without.
I’m caramelizing the onions the same way as I usually do. Just thinly sliced onions, a pinch of thyme, a tablespoon of sugar, and a little balsamic. I love the flavor that balsamic vinegar adds to caramelized onions. And trust me, it works well in this casserole. The onions are sautéed with minced garlic to bring a little somethin’ somethin’ of their own to the table. And the cheese! I had a ton of gruyere on hand after making this and some provolone tucked away in the freezer. So I did a combination of both. But mozzarella cheese would work really well too. In fact, any kind of cheese that’s made for melting would do the trick.
What I love the most about this breakfast though is that it’s all there. In one dish. Everything. Your bread, your toppings, your cheese. It’s a hearty, filling meal that requires little fluff on the side. And by fluff, I mean, you don’t need to toast your bread, or scramble up eggs, or whatever else. It’s all in one dish. Breakfast casseroles are perfect for serving to larger crowds because they make a TON and require minimum work. I baked mine in a round dish but baking it in a 9×13 dish will easily feed 6-8 people. Yup! Just serve it up simple with fresh fruit, some muffins or croissants on the side. And coffee. Always, lots of coffee.
Now there are ways to make this even heartier. Just like my veggie-loaded breakfast casserole, this savory french toast is customizable too. If you would like to add in some extra protein, brown some sausage, ground turkey, or chicken before adding it in as a layer into this casserole. It’s that simple. I’d put it in between the bread and the veggies.
There’s a big piece of this savory french toast in the refrigerator that’s calling my name. A warm
cup vat of coffee and i’m in heaven! Like I said, this makes a ton, so I boxed some up and took it over to our ex-neighbors/besties. They just moved so with all the chaos they are now dealing with, I knew it would be a hearty breakfast to keep their energy up.
My slice in calling my name, but TRY THIS. You’ll be glad you did 🙂
- ¾ loaf (day old) french bread, diced
- 2 medium onions, halved and thinly sliced
- 2 tablespoons butter, divided
- 1 tablespoon oil
- ½ teaspoon fresh thyme (or ¼ dried)
- 1 tablespoon granulated sugar
- ½ tablespoon balsamic vinegar
- 2 teaspoons minced garlic
- 4 ounces fresh baby spinach, roughly chopped
- 1 ¼ cup milk (I swapped out ¼ cup for heavy cream)
- 8 large eggs
- 4 ounces crumbled feta cheese
- 1 ½ cup shredded cheese*
- Heat 1 tablespoon of butter and oil in a large cast iron skillet over medium heat. Add the onions and let sauté for 5 minutes, stirring as required. Add the thyme and sugar and continue to cook for 20-25 minutes on medium low heat. Be sure to stir the onions every 5 minutes so they caramelize evenly. If at any point the onions are caramelizing too fast, turn down the heat to the low setting. Add the balsamic vinegar to deglaze the pan, allow the onions to soak it all in. Remove the onions to a plate.
- While the onions are caramelizing, in a large bowl, whisk together the eggs, milk, crumbled feta cheese, and salt and pepper to preference. Set aside.
- Add the remaining 1 tablespoon of butter to the skillet. Add the garlic and allow it to saute for 30 seconds or until it becomes fragrant. Add the spinach and let it cook down until just wilted; about 1-2 minutes. Remove spinach to the same plate as the onions. Toss to mix evenly.
- Position a rack in the center of the oven and preheat the oven to 375ºF if you are baking the casserole immediately. Generously spray a 9x13 baking dish with nonstick cooking spray. Add the diced french bread into the dish and press gently so the bread flattens a bit. Add the onion and spinach mixture on top, spreading it evenly. Using the back of a large spoon, press down the mixture down a bit so that it's not popping out over the dish. Pour the egg mixture over the prepared casserole. Sprinkle with the cheese and another small pinch of salt and pepper.
- Bake the casserole, uncovered until the cheese melts, and the top gets all nice and golden, 45-50 minutes. Allow the casserole to cool for 10 minutes before slicing and serving.
- Make-ahead: prepare the casserole as directed, cover with plastic wrap and refrigerate overnight or as required (not to exceed 24 hours) and allow it to come to room temperature for 20 minutes before baking.
- Other add-ins: I kept this recipe vegetarian, but you can certainly add in browned sausage, ground turkey/beef, shredded chicken, or ham. Though I love and suggest the nutty flavor of gruyere for this casserole, other cheese that would be good - mozzarella, pepper jack, white cheddar, or provolone.