Buttery Croissant Breakfast Casserole

This eggs and cheese croissant casserole transforms buttery bakery favorites into a decadent breakfast that's perfect for weekend brunches or holiday mornings. The croissants soak up the savory egg mixture while two kinds of cheese create pockets of melty goodness throughout the dish.

I first made this for a Christmas morning breakfast when my in-laws were visiting. The kitchen filled with an irresistible aroma while we opened presents, and it has become our holiday tradition ever since.

Ingredients

• Buttery croissants provide the rich base and create beautiful layers as they bake
• Swiss cheese melts perfectly and adds a nutty flavor that complements the buttery croissants
• Parmesan cheese creates a golden crispy top layer
• Eggs and milk form the custard that holds everything together
• Dried thyme adds an earthy herbal note that elevates the savory flavors
• Garlic powder infuses subtle aromatic flavor throughout the casserole
• Fresh chives bring a bright pop of color and mild onion flavor to finish the dish

Step-by-Step Instructions

Prepare the Baking Dish

Grease your 9x13 inch baking dish thoroughly to prevent sticking. The butter adds additional flavor while ensuring easy serving later. Use a paper towel to spread butter or a good quality cooking spray evenly across the bottom and sides.

Layer the Base

Arrange the quartered croissant pieces evenly throughout the baking dish. Tear some pieces slightly to fill any large gaps. The varying sizes create interesting texture differences in the final dish. Some pieces will remain crisp while others become wonderfully custardy.

Add the First Cheese Layer

Distribute the shredded Swiss cheese evenly over the croissant pieces. Make sure to get cheese into the crevices between croissant pieces for pockets of melted goodness throughout the casserole. The Swiss cheese adds a subtle nutty flavor that pairs perfectly with the buttery croissants.

Create the Custard Mixture

In a large bowl, whisk the eggs vigorously until well beaten. Add the milk gradually while continuing to whisk. Incorporate the thyme, garlic powder, salt and pepper, whisking until the mixture is completely uniform. The herbs should be evenly distributed throughout the liquid.

Combine Components

Pour the egg mixture slowly over the croissant and cheese layers, allowing time for absorption. Use the back of a spoon or spatula to gently press the croissants down into the liquid. This ensures even soaking and prevents dry spots in your finished casserole.

Top with Parmesan

Sprinkle the Parmesan cheese evenly across the top of the casserole. The Parmesan will create a beautiful golden crust during baking. Make sure to reach the edges of the dish for consistent flavor in every portion.

Bake to Perfection

Cover the dish with foil for the initial bake to prevent over-browning while the custard sets. Removing the foil for the final cooking time allows the top to become beautifully golden and slightly crisp. The casserole is done when the center is set but still slightly jiggly.

Bookmark

The thyme in this recipe makes all the difference in transforming this from a simple casserole to something special. My grandmother always used fresh herbs from her garden, but I've found that dried thyme works wonderfully when fresh isn't available. The aroma as it bakes reminds me of Sunday mornings at her house.

Make-Ahead Instructions

This casserole is perfect for preparing in advance. Assemble the entire dish up to 24 hours before baking, cover tightly with plastic wrap, and refrigerate. Remove from the refrigerator 30 minutes before baking to take the chill off. You may need to add 5-10 minutes to the covered baking time since the ingredients will be cold.

Ingredient Substitutions

Day-old bread can replace croissants for a more traditional bread pudding style casserole. Brioche, challah, or French bread all work beautifully. The texture will be slightly denser but equally delicious.

Any melting cheese works well in place of Swiss. Try Gruyère for a more intense flavor, fontina for extra creaminess, or cheddar for a sharper taste. The Parmesan can be replaced with Romano or Asiago for a similar salty finish.

For a dairy-free version, use plant-based butter, non-dairy milk, and your favorite melting vegan cheese alternatives. The texture will be slightly different but still satisfying.

Serving Suggestions

This versatile casserole pairs beautifully with fresh fruit for a complete breakfast. A simple mixed berry salad with mint provides a refreshing contrast to the rich casserole.

For a special brunch, serve alongside mimosas or a bloody mary bar. The savory flavors of the casserole complement cocktails perfectly.

Add a simple green salad dressed with lemon vinaigrette for a complete meal when serving this for lunch or a light dinner.

Recipe FAQs

→ Can I prepare this croissant casserole the night before?

Yes! This dish works wonderfully as an overnight preparation. Assemble everything the night before, cover tightly with plastic wrap, and refrigerate. In the morning, remove from the refrigerator 30 minutes before baking to take the chill off, then bake as directed, possibly adding 5-10 minutes to the covered baking time.

→ What can I substitute for Swiss cheese?

Gruyère makes an excellent substitute with its nutty flavor. Other good alternatives include Emmental, Fontina, Gouda, or even Monterey Jack if you prefer a milder flavor. The key is choosing a cheese that melts well.

→ How can I tell when the casserole is fully cooked?

The casserole is done when the center is set and no longer jiggly, the top is golden brown, and a knife inserted in the center comes out clean without raw egg mixture. The internal temperature should reach 160°F (71°C) for food safety.

→ Can I add vegetables or meat to this dish?

Absolutely! Sautéed mushrooms, spinach, bell peppers, or caramelized onions work beautifully. For meat additions, try cooked and crumbled bacon, diced ham, or browned sausage. Just make sure any additions are pre-cooked to remove excess moisture before adding to the casserole.

→ How should I store and reheat leftovers?

Store leftovers in an airtight container in the refrigerator for up to 3 days. Reheat individual portions in the microwave for 1-2 minutes until warmed through. For best texture, reheat larger portions in a 325°F (165°C) oven, covered with foil, for about 15-20 minutes until heated through.

→ Can I freeze this croissant casserole?

Yes, you can freeze this casserole either before or after baking. If freezing unbaked, assemble completely, cover tightly with plastic wrap and foil, and freeze for up to 1 month. Thaw overnight in the refrigerator before baking. If freezing after baking, cool completely, wrap portions tightly, and freeze for up to 2 months. Thaw and reheat in a 325°F oven until hot throughout.