This Croissant Breakfast Casserole will surely feed a crowd. It's loaded with sausage, egg, and cheese and croissants for a hearty breakfast. You'll love this croissant egg bake!
Lightly oil a 9x13 baking dish. Cut each croissant into 4 pieces. Arrange the croissants evenly in the pan. I like to arrange the croissants so some of the ends are sticking up and you can easily tell that it is a croissant casserole.
Sauté the onions in large skillet on medium-high heat with a little oil (about ½ tablespoon) for about 3 minutes, until they start to soften. Add in the sausage meat and cook until the sausage meat is cooked through and browned. Break the sausage meat into small pieces with a spatula as it cook. Add in the chopped lacinato kale and sauté for an additional minute, until it starts to wilt. Remove pan from heat.
Whisk the eggs, milk, salt, ground black pepper, cayenne, sage (if using), and rosemary (if using) together in a large bowl. Set aside.
Layer the sausage mix on top of the croissant pieces. Arrange the sausage pieces so they fill in the gaps between the croissants. You may also need to arrange the kale so the green is evenly spread out over the casserole.
Evenly layer the grated cheese on top of the sausage mix. Gently pour the egg mixture on top, pouring over all the croissant pieces, including the pieces that may be sticking out. Let the casserole sit for about 5-10 minutes before baking.
Preheat the oven to 325°/160°C. Place the casserole in the middle of the oven. Bake for 30 minutes. Turn the heat up to 350°C/176°C. Bake for an additional 20-30 minutes, until the eggs are set. To check, insert a knife in the middle of the croissant casserole and it should come out clean. If the casserole is browning too quickly, cover with a foil for the last bit of baking time.
Let the casserole sit for 10 minutes before cutting and serving.