Buttery Breakfast Casserole

Why You’ll Love This Recipe

I love this recipe because it takes classic breakfast ingredients and transforms them into a luxurious, hearty casserole that’s easy to prepare ahead of time. Toasting the croissants adds a wonderful caramelized flavor that holds up beautifully against the savory sausage and fragrant sage. The Gruyère cheese melts throughout, creating a creamy texture and a delicious crust on top. It’s one of my go-to dishes for holiday mornings or weekend brunches when I want to impress with minimal effort.

Ingredients

• 1 pound croissants (about 5 to 7), split in half lengthwise

• 1 tablespoon extra-virgin olive oil, plus more for greasing the baking dish

• 1 bunch scallions (6 to 7), white and light green parts thinly sliced, greens reserved

• ¾ pound sweet Italian sausage, casings removed

• 2 teaspoons finely chopped fresh sage

• 8 large eggs

• 3 cups whole milk

• 1 cup heavy cream

• 8 ounces Gruyère cheese, grated (about 2 cups)

• 1¼ teaspoons kosher salt

• 1 teaspoon black pepper

(Here’s a tip: Check out the full list of ingredients and measurements in the recipe card below.)

Directions

1. Preheat the oven to 500°F (260°C). Arrange croissants cut side up on a large baking sheet and toast until golden brown, about 5 to 10 minutes, watching carefully to avoid burning. Let cool, then tear into large bite-sized pieces.

2. In a medium skillet over medium-high heat, warm olive oil. Add the sliced scallions and sausage meat, cooking and breaking up the sausage with a fork until browned, about 5 minutes. Stir in chopped sage and remove from heat.

3. In a large bowl, toss the toasted croissant pieces with the sausage mixture.

4. In a separate bowl, whisk together eggs, milk, cream, 1½ cups of the grated Gruyère, salt, and black pepper.

5. Lightly oil a 9 x 13-inch baking dish. Spread the croissant and sausage mixture evenly in the dish. Pour the custard mixture over, pressing down gently on the croissants to help them absorb the liquid. Cover with plastic wrap and refrigerate for at least 4 hours or overnight.

6. When ready to bake, preheat the oven to 350°F (175°C). Sprinkle the remaining ½ cup Gruyère cheese evenly over the top of the casserole.

7. Bake uncovered for about 45 minutes, or until the casserole is golden brown and firm to the touch. Let stand for 10 minutes before serving. Garnish with the reserved scallion greens.

Servings and Timing

This casserole serves 8 to 10 people. Total time includes about 10 minutes prep, at least 4 hours chilling, and 45 minutes baking.

Variations

• Substitute spicy Italian sausage for a bit of heat.

• Add sautéed mushrooms, bell peppers, or spinach for extra veggies.

• Use sharp cheddar or fontina cheese instead of Gruyère for a different flavor profile.

• Mix in fresh herbs like thyme or rosemary alongside sage.

• For a dairy-free option, substitute milk and cream with plant-based alternatives and omit cheese.

Storage/Reheating

Leftovers keep well refrigerated in an airtight container for up to 3 days. Reheat in the oven at 350°F until warmed through, about 15–20 minutes. This casserole also freezes well—freeze before baking and thaw overnight in the fridge before baking as directed.

FAQs

Can I prepare this casserole entirely the day before?

Yes, preparing it the night before and baking in the morning is perfect and allows the flavors to meld.

Can I use other bread instead of croissants?

Yes, buttery brioche or challah work well as a substitute, though the texture will vary slightly.

Is this recipe suitable for meal prep?

Absolutely! It reheats nicely and makes great leftovers for breakfast or lunch.

Can I make this vegetarian?

Omit the sausage and add sautéed vegetables like mushrooms and spinach instead.

How do I store leftovers properly?

Cover tightly with plastic wrap or store in an airtight container in the fridge for up to 3 days.

Conclusion

Buttery Breakfast Casserole is my favorite way to elevate breakfast or brunch with minimal effort. The combination of toasted croissants, savory sausage, fresh herbs, and creamy Gruyère cheese creates a rich, satisfying dish that’s sure to impress. It’s perfect for special occasions or any time I want a comforting, make-ahead breakfast.

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