Description

This Sausage and Sage Croissant Breakfast Casserole is a deliciously savory morning dish combining buttery croissants, sweet Italian sausage, fresh sage, and creamy Gruyère cheese baked into a custardy casserole. It’s perfect for brunch gatherings or make-ahead breakfasts, soaking overnight to meld flavors and bake to golden perfection. The rich custard and crispy croissant pieces create a satisfying comfort food with a fresh herbal brightness.

Ingredients

Scale

Casserole Base and Toppings

1-2 tablespoons butter, softened (for greasing dish)
1 pound croissants (about 5 to 7), split in half lengthwise
1/2 cup Gruyère cheese, grated (for topping)
Reserved green parts of scallions (for garnish)
1 tablespoon fresh sage, finely chopped (for garnish)

Sausage Mixture

1 tablespoon vegetable oil
3/4 pound sweet Italian sausage, casings removed
1 bunch scallions (6 to 7), white and light green parts thinly sliced
2 teaspoons fresh sage, finely chopped

Egg Custard

8 large eggs, at room temperature
3 cups whole milk
1 cup heavy cream
1 1/2 cups Gruyère cheese, grated
1 1/4 teaspoons salt
1 teaspoon black pepper

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Instructions

Grease Baking Dish: Use 1-2 tablespoons of softened butter to generously grease a 9×13 inch baking dish. Set it aside. Preheat your oven to 350ºF (177ºC).
Toast Croissants: Arrange croissant halves cut side up on a large baking sheet. Bake for 2 to 4 minutes until golden brown, then remove and let cool until manageable. Tear the croissants into large bite-sized pieces.
Cook Sausage: Heat 1 tablespoon vegetable oil in a skillet over medium-high heat. Add the sweet Italian sausage, cooking and crumbling it until well browned and cooked through, about 6-8 minutes.
Add Scallions: Stir in the sliced white and light green scallion parts into the sausage mixture. Continue cooking until scallions are softened.
Incorporate Sage and Cool: Mix in 2 teaspoons of finely chopped fresh sage. Remove the skillet from heat and let the sausage mixture cool for 7-10 minutes to avoid cooking the eggs later.
Combine Croissants and Sausage Mixture: In a large bowl, toss together the toasted croissant pieces and cooled sausage mixture to evenly distribute flavors.
Prepare Egg Custard: In a separate large mixing bowl, whisk together 8 large eggs, 3 cups whole milk, 1 cup heavy cream, 1 1/2 cups grated Gruyère, 1 1/4 teaspoons salt, and 1 teaspoon black pepper until fully combined and smooth.
Assemble Casserole: Pour the croissant and sausage mixture into the buttered baking dish and spread evenly. Pour the egg mixture over the top, gently pressing down the croissants so they absorb the liquid well.
Refrigerate: Cover the assembled casserole tightly with plastic cling wrap. Refrigerate for at least 4 hours or overnight to let the custard soak thoroughly into the croissants and flavors meld.
Preheat Oven for Baking: When ready to bake, preheat your oven again to 350ºF (177ºC).
Bake Casserole: Remove the plastic wrap. Sprinkle the remaining 1/2 cup Gruyère cheese on top of the casserole. Bake uncovered for about 45 minutes or until the top is golden brown and the center is firm to the touch. Remove from oven and let sit for 10 minutes before serving.
Garnish and Serve: Top the casserole with the reserved scallion greens and 1 tablespoon of chopped fresh sage for a fresh accent. Serve warm and enjoy your flavorful breakfast casserole.

Notes

The casserole benefits from soaking overnight to allow the croissants to absorb the custard fully, improving texture and flavor.
You can substitute Gruyère cheese with Swiss or Emmental cheese if preferred.
Make sure the sausage mixture cools before combining with eggs to prevent scrambling the eggs prematurely.
If fresh sage is unavailable, use 1 teaspoon dried sage but reduce slightly.
Leftovers keep well refrigerated for up to 3 days and can be reheated in the oven or microwave.