1. Do I have to let the casserole sit overnight?

No, but letting it rest overnight enhances the flavor and texture. Even a few hours of chilling helps the custard fully absorb into the croissants.

2. What is a good substitute for Gruyère cheese?

Swiss cheese or white cheddar work wonderfully if Gruyère isn’t available. Smoked gouda adds a deeper, savory note.

3. What can I make with old croissants?

Besides this Croissant Breakfast Casserole , you can use them in bread pudding, French toast bakes, or savory strata.

4. What do the French eat with croissants for breakfast?

Typically, coffee, jam, or fruit. This casserole reimagines that tradition by combining croissants with custard and cheese in a single dish.

5. What to serve with croissant breakfast casserole?

It pairs beautifully with fresh fruit, a light salad, or sweet treats like my chocolate silk pie and pecan pie bars recipe .

6. How do you make a simple breakfast casserole?

Mix eggs, milk, cheese, and your favorite fillings. Pour over bread or croissants, then bake until golden and set.

Croissant Breakfast Casserole With Mushroom And Gruyère Recipe Easy (2025)

Description

This Croissant Breakfast Casserole with Mushroom and Gruyère is a make-ahead masterpiece that combines buttery croissants, creamy Gruyère cheese, and savory mushrooms in one comforting bake. Perfect for holidays, brunch gatherings, or slow weekend mornings.

Ingredients

4 tablespoons unsalted butter, plus more for the baking dish
1 pound mixed wild mushrooms, finely chopped
2 garlic cloves, minced
1 large shallot, thinly sliced
2 tablespoons fresh thyme leaves
Kosher salt and freshly ground black pepper
1 tablespoon sherry vinegar
4 ounces cream cheese, diced and softened
8 ounces Gruyère cheese, shredded (about 2 cups)
2 scallions, thinly sliced crosswise
10 large eggs
1 1/4 cups half-and-half
1 tablespoon plus 5 teaspoons Dijon mustard
10 small plain croissants, halved lengthwise

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Instructions

Sauté the Mushrooms: Melt the butter in a large skillet over medium heat. Add mushrooms, garlic, shallot, thyme, salt, and pepper. Cook for 5 minutes until tender and browned.
Deglaze and Cool: Stir in the sherry vinegar, scraping up any brown bits. Transfer to a bowl and let cool for 5 minutes.
Mix the Filling: Add the cream cheese, 1 cup Gruyère, and half the scallions to the mushrooms. Stir until combined.
Make the Custard: Whisk eggs, half-and-half, Dijon, remaining scallions, salt, and pepper in a separate bowl until smooth.
Assemble the Casserole: Grease a 9×13-inch baking dish with butter. Spread 1/2 teaspoon Dijon on each croissant half. Arrange bottoms in the dish, layer the mushroom mixture, and cover with croissant tops.
Add Custard and Chill: Pour the egg mixture evenly over the croissants, sprinkle with remaining Gruyère, then cover and refrigerate for at least 4 hours or overnight.
Bake and Serve: Preheat oven to 350°F. Bake covered for 30 minutes, then uncover and bake 15 more until golden and set. Let rest 5 minutes before serving.

Notes

Use day-old croissants for best texture. Let the casserole rest before slicing for clean layers. Add caramelized onions or spinach for variation. Prepare ahead as an overnight bake for stress-free mornings.

Prep Time: 40 minutes
Cook Time: 45 minutes
Category: Main Dish
Method: Baking
Cuisine: French-Inspired