Description

A rich and flavorful breakfast casserole featuring buttery croissants, savory sweet Italian sausage, fragrant fresh sage, and creamy Gruyère cheese. This make-ahead dish is soaked overnight in an egg custard and baked to golden perfection, making it an ideal hearty breakfast or brunch dish that combines comforting textures and fresh herbaceous accents.

Ingredients

Scale

For the Casserole Base

1-2 tablespoons butter, softened
1 pound croissants (about 5 to 7), split in half lengthwise
1 tablespoon vegetable oil
1 bunch scallions (6 to 7), white and light green parts thinly sliced, greens reserved
3/4 pound sweet Italian sausage, casings removed
2 teaspoons fresh sage, finely chopped

For the Egg Custard

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

For Garnish

1/2 cup Gruyère cheese, grated
1 tablespoon fresh sage, finely chopped
Reserved green parts of scallions

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Instructions

Grease Baking Dish: Generously butter a 9×13 inch baking dish using 1-2 tablespoons of softened butter and set it aside. Preheat your oven to 350ºF (177ºC) to prepare for toasting the croissants.
Toast Croissants: Arrange the croissant halves cut side up on a large baking sheet. Bake them for 2 to 4 minutes until they turn golden brown. Remove from oven and allow to cool until they can be handled easily, then tear into large bite-sized pieces.
Cook Sausage: Heat 1 tablespoon of vegetable oil in a skillet over medium-high heat. Add the sweet Italian sausage, breaking it apart and cooking until well browned and thoroughly cooked through, approximately 6-8 minutes.
Add Scallions: Stir in the thinly sliced white and light green parts of scallions into the cooked sausage. Continue to cook until the scallions soften, blending their mild onion flavor with the sausage.
Incorporate Sage and Cool: Mix in 2 teaspoons of finely chopped fresh sage into the sausage and scallion mixture. Remove the skillet from heat and let it cool for 7 to 10 minutes. Cooling prevents the eggs from cooking prematurely when combined later.
Combine Croissants and Sausage Mixture: In a large mixing bowl, toss together the toasted croissant pieces with the cooled sausage mixture to ensure flavors are evenly distributed.
Prepare Egg Custard: In a separate large bowl, whisk together 8 large eggs, 3 cups whole milk, 1 cup heavy cream, 1 1/2 cups grated Gruyère cheese, 1 1/4 teaspoons salt, and 1 teaspoon black pepper until the mixture is smooth and fully combined.
Assemble Casserole: Pour the croissant and sausage mixture into the prepared buttered baking dish, spreading it evenly. Pour the egg custard over the top, gently pressing the croissant pieces down so they soak up the liquid well.
Refrigerate: Cover the assembled casserole tightly with plastic cling wrap. Refrigerate for at least 4 hours or preferably overnight, allowing the custard to soak thoroughly into the croissants and the flavors to meld beautifully.
Preheat Oven for Baking: When ready to bake, preheat your oven again to 350ºF (177ºC).
Bake Casserole: Remove the plastic wrap from the casserole. Sprinkle the remaining 1/2 cup of grated Gruyère cheese evenly on top. Bake uncovered for about 45 minutes or until the surface is golden brown and the center is firm to the touch. Remove from oven and let rest for 10 minutes before serving.
Garnish and Serve: Garnish the casserole with the reserved green parts of scallions and 1 tablespoon of freshly chopped sage. Serve warm to enjoy the harmonious combination of savory sausage, creamy custard, and fresh herbs.

Notes

Using day-old croissants can enhance texture as they absorb the custard better without becoming overly soggy.
Allowing the casserole to rest refrigerated overnight intensifies the flavor and improves soaking, but 4 hours is the minimum for good results.
Room temperature eggs prevent curdling when mixed with the cold dairy ingredients.
Gruyère cheese can be substituted with Swiss or Emmental for a similar melty texture and nutty flavor.
Make sure to cool the sausage mixture before combining it with the eggs to avoid cooking the eggs prematurely.