This French onion croissant bake is ideal for a special breakfast or holiday brunch. Prepare it ahead, refrigerate overnight, and bake just before serving. Savory, cheesy and utterly delicious.
Why is holiday brunch so delightful?
This overnight French onion croissant bake truly feels like a holiday treat. It’s made ahead of time, rich and indulgent, and elegant enough for a festive table while also feeding a crowd.
It hits all the marks for a memorable holiday meal.
I first fell in love with this style of overnight croissant breakfast bake a few years ago. We only make it on special occasions because it’s filling and decadent, and it’s one of the few dishes that everyone seems to adore. We look forward to it every holiday morning.
This year I gave the casserole a French onion twist: I reduced the spinach and added heaps of caramelized onions. The result is exactly as delicious as it sounds.
How I make it
The process starts with slowly caramelizing a few large sweet onions. That step takes time—plan for 60 to 90 minutes—but it’s worth the attention. Begin over medium heat to get things moving, then reduce to low and let the onions develop a deep golden, sweet, caramelized flavor. If they dry out or begin to stick, add a splash of water as needed.
One of the best parts of this dish is the croissant base. I toast croissants under the broiler until they pick up crisp, caramelized edges; those crunchy bits soak up the custard and give the bake great texture.
The custard is a simple, rich mix of eggs, milk, heavy cream and freshly grated gruyère. The cheese melts into the custard and creates a silky, soufflé-like interior.
Once the croissants are toasted and torn into pieces, everything gets combined: croissant pieces, caramelized onions, eggs, dairy and cheese. Cover and refrigerate overnight so the croissants fully absorb the custard—this step is essential for the proper texture.
In the morning, bring the dish out of the fridge, top with the remaining grated cheese and bake until golden and set. The finished bake is cheesy, melty, crisp on top and soft inside, with a balance of savory and sweet from the onions.
The top browns beautifully in the oven and the croissant pieces puff and soak up the custard, creating a tender, slightly airy texture.
Just look at that golden color and texture.
This makes a lovely holiday brunch or a satisfying meal to enjoy after a relaxed day. It serves many people and always feels special.
It’s one of my favorite things to serve—and one of the best things I’ve tasted.
French Onion Croissant Bake
Overnight French Onion Croissant Bake
Ingredients
- 3 tablespoons olive oil
- 4 large sweet onions, thinly sliced
- Kosher salt and pepper
- 5 to 7 large croissants, sliced in half lengthwise
- 2 garlic cloves, minced
- 8 large eggs
- 2 1/2 cups milk
- 1 cup heavy cream
- 8 ounces gruyère cheese, freshly grated
- 3 tablespoons chopped fresh thyme, plus more for topping
- Parmesan cheese for topping
Instructions
- Heat the olive oil in a large oven-safe skillet over medium heat. Add the sliced onions and a large pinch of salt. Cook, stirring often, until they soften, about 10 to 15 minutes.
- Reduce the heat to low or medium-low and continue to cook the onions, stirring frequently, until deeply golden and caramelized, about 60 to 90 minutes. If they begin to stick or brown too quickly, lower the heat or add a splash of water.
- When the onions are deeply caramelized, transfer them to a plate. (If you’re short on time, 1 teaspoon of sugar or honey speeds caramelization—stir and watch carefully.)
- Preheat the oven to 450°F. Place croissants cut-side up on a baking sheet and toast 5 to 8 minutes until crisp and golden. Let cool slightly, then tear or chop into pieces.
- Brush a 9×13-inch baking dish with melted butter. Scatter the croissant pieces in the dish and toss with half of the caramelized onions to distribute them evenly.
- In a large bowl, whisk together eggs, milk, heavy cream, salt and pepper. Stir in 1 cup of gruyère and the chopped herbs if using. Reserve the remaining cheese in the fridge.
- Pour the custard over the croissants, pressing pieces down so they absorb the liquid. Top with the remaining caramelized onions.
- Cover with plastic wrap and refrigerate for 8 hours or overnight.
- Preheat the oven to 350°F and remove the dish from the fridge 30 minutes before baking to take the chill off.
- Uncover, top with the reserved grated cheese, and bake uncovered for 45 to 60 minutes, until the center is set and the top is golden. Sprinkle with parmesan and fresh thyme before serving.
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Happy holidaying!