Can You Use Store-Bought Croissants?

Yes— store-bought croissants work perfectly . In fact, day-old ones are ideal because they toast better and soak up the custard mix more efficiently.

What If I Don’t Have Heavy Cream?

You can substitute with additional whole milk or even evaporated milk, though the final texture will be slightly less rich.

Do I Have to Let It Sit Overnight?

Technically, 4–6 hours in the fridge can work, but the texture and flavor develop best with a full 8-hour soak . It gives the croissants time to fully absorb the egg mixture.

Can I Make This in a Smaller Dish?

Yes—halve the recipe and bake in an 8x8-inch dish. Just reduce the bake time by about 5–10 minutes and keep an eye on the top browning.

Overnight Croissant Breakfast Bake – The Best Cozy Holiday Casserole

Name: Overnight Croissant Breakfast Bake
Prep time: 45 min
Cook time: 45 min
Total time: 9 h 30 min
Cuisine: American
Ingredients: 5 to 7 large croissants, sliced in half lengthwise; 2 tablespoons unsalted butter; 1 sweet onion, diced; 2 garlic cloves, minced; 10 ounces cremini mushrooms, chopped; 8 ounces fresh baby spinach; Kosher salt and pepper; 8 large eggs; 2 ½ cups milk; 1 cup heavy cream; 8 ounces gruyere cheese, freshly grated; Fresh chopped parsley, for topping; Parmesan cheese, for topping

Description

A rich and savory make-ahead breakfast casserole made with toasted croissants, creamy egg custard, sautéed vegetables, and melty gruyere cheese – perfect for holidays or brunch.

Ingredients

Scale

5 to 7 large croissants, sliced in half lengthwise
2 tablespoons unsalted butter
1 sweet onion, diced
2 garlic cloves, minced
10 ounces cremini mushrooms, chopped
8 ounces fresh baby spinach
Kosher salt and pepper
8 large eggs
2 ½ cups milk
1 cup heavy cream
8 ounces gruyere cheese, freshly grated
Fresh chopped parsley, for topping
Parmesan cheese, for topping

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Instructions

Preheat the oven to 450°F. Place croissants cut-side up on a baking sheet and toast for 5–8 minutes until golden. Let cool, then tear into pieces.
In a skillet, melt butter over medium-low heat. Add onions and garlic and sauté for 5 minutes.
Add mushrooms and cook for another 5 minutes until soft and browned.
Stir in spinach and cook until wilted. Season with salt and pepper.
Grease a 9×13-inch baking dish with butter. Combine toasted croissants and veggie mix in the dish.
In a large bowl, whisk together eggs, milk, heavy cream, salt, pepper, and 1 cup grated cheese.
Pour egg mixture over croissant mixture. Press croissants into the liquid to absorb.
Cover tightly with plastic wrap and refrigerate overnight (at least 8 hours).
Remove dish from fridge 30 minutes before baking. Preheat oven to 350°F.
Top with remaining cheese and bake uncovered for 45 minutes, until golden and set.
Garnish with parmesan and parsley before serving.

Notes

Day-old croissants work best for texture and absorption.
Let the dish sit at room temp before baking to ensure even cooking.
You can freeze the unbaked or baked casserole for up to 2 months.
Customize with sausage, bacon, or different cheeses.

Prep Time: 45 minutes
Cook Time: 45 minutes
Category: Breakfast
Method: Baking
Cuisine: American

Nutrition

Serving Size: 1 slice
Calories: 420–480
Sugar: 4g
Sodium: 620mg
Fat: 30g
Saturated Fat: 16g
Unsaturated Fat: 12g
Trans Fat: 0.5g
Carbohydrates: 32g
Fiber: 2g
Protein: 20g
Cholesterol: 220mg