Caramelized Onion, Prosciutto, Brie, & Swiss Croissant Breakfast Casserole
In this Prosciutto, Brie, & Swiss Croissant Breakfast Casserole, lightly toasted croissants, salty prosciutto, creamy brie, and sweet caramelized onions are mixed with a rich, eggy custard and topped with buttery Swiss cheese, creating a rich and decadent casserole. With the option to make ahead, it is sure to impress for any breakfast or brunch.
Servings: 8
Ingredients
- 10 oz day-old croissants (about 12 mini croissants or 6 regular)
- 4 tablespoons unsalted butter (divided)
- 2 medium white onions (thinly sliced)
- kosher salt and pepper
- 2 cloves garlic (minced or grated)
- 2 teaspoons dried thyme
- 1 cup heavy cream
- 1 cup milk
- 4 eggs (beaten)
- 2 tablespoons dijon mustard
- 1/2 teaspoon cayenne pepper (more or less to taste)
- 4 ounces prosciutto (torn)
- 4 ounces creamy Brie cheese (rind cut off & cubed)
- 1 cup Swiss cheese (shredded)
- 2 tablespoons everything bagel seasoning
Instructions
- Preheat the oven to 350°
- In a heavy skillet, melt 2 tablespoons butter over medium heat. Add the sliced onions and stir to coat the onions in the butter. Cover and cook 15 minutes, stirring after about 7 minutes to make sure they don’t burn. Uncover onions, and continue to cook 5 – 10 more minutes until the onions are soft and caramelized. Add the garlic and thyme, cook an additional minute. Remove from the heat and set aside.
- While the onions cook, grease a 9 x 13-inch baking dish with cooking spray. Roughly tear croissants into medium size chunks. Arrange the torn croissants in the baking dish and lay 2 tablespoons of thinly sliced butter over the croissants. Transfer to the oven and bake 5-8 minutes, until the croissants are lightly toasted.
- In a large bowl, whisk together the cream, milk, eggs, mustard, cayenne, and a pinch each of salt and pepper. Add the toasted croissants, onions, prosciutto, and Brie, gently stir to combine. Pour the mixture back into the casserole dish. Top with Swiss cheese and sprinkle with everything seasoning.
- Cover with foil and bake for 30 minutes. Remove the foil, and continue baking for another 10-15 minutes or until the croissants are golden on top. Serve warm.
Notes
To Make a Few Hours Ahead: This can be prepped and assembled a few hours ahead of time and kept in the fridge. But keep in mind, you don’t want to let the croissants sit in the custard for more than 1 – 2 hours, as they will break down too much and become soggy.
To Make the Night Before: Complete the recipe through step 3. For step 4, keep the croissants separate (I just store mine in the Pyrex casserole dish with the lid on). Keep the custard mixture (without the croissants) in a sealed container in the fridge. When ready to assemble, remove from the fridge and toss the croissants with the egg mixture, then assemble in baking dish. Bake as directed.
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