If you are looking for a luxurious and satisfying breakfast that will wow your family or guests, this Overnight Croissant Breakfast Bake is the ultimate solution. Combining buttery croissants, savory vegetables, rich eggs, and melty gruyere cheese, this dish is decadent, hearty, and perfect for a special morning or a holiday gathering. The beauty of this recipe is that it can be prepared the night before, refrigerated, and then baked fresh in the morning, filling your kitchen with irresistible aromas that make breakfast feel like a celebration.
The foundation of this dish is flaky, buttery croissants that are toasted to perfection. Their crisp exterior and tender interior provide a decadent base for the soft, creamy egg custard and the medley of vegetables and cheese. Spinach and mushrooms are sautéed with onions and garlic to create a savory filling that perfectly complements the richness of the croissants and the custard. Freshly grated gruyere cheese melts into the mixture, creating pockets of creamy, gooey flavor throughout the bake. This Overnight Croissant Breakfast Bake is indulgent, satisfying, and truly one of the most delicious breakfast casseroles you will ever make.
Ingredients
Croissant Base:
- 5 to 7 large croissants, sliced in half lengthwise
- 2 tablespoons unsalted butter
Vegetable Filling:
- 1 sweet onion, diced
- 2 cloves garlic, minced
- 10 ounces cremini mushrooms, chopped
- 8 ounces fresh baby spinach
- Kosher salt and freshly ground black pepper, to taste
Egg Custard:
- 8 large eggs
- 2 ½ cups milk
- 1 cup heavy cream
- 8 ounces gruyere cheese, freshly grated
- Optional: 2 tablespoons fresh chopped parsley, 1 tablespoon chives, finely chopped
Topping:
- Additional grated gruyere cheese, as desired
- Parmesan cheese, for sprinkling
- Fresh parsley, for garnish
Equipment Needed
- Baking sheets
- 9×13-inch baking dish
- Large skillet or frying pan
- Large mixing bowls
- Whisk
- Rubber spatula
- Knife and cutting board
- Plastic wrap
- Oven
Step-by-Step Instructions
Step 1: Preheat Oven and Toast Croissants
Preheat your oven to 450°F (230°C). Slice the croissants in half lengthwise and arrange them cut-side up on a baking sheet. Toast them in the oven for 5 to 8 minutes, until they are golden brown and slightly crisp. This step adds a delightful caramelized flavor and ensures that the croissants maintain texture when soaked in the egg custard. Once toasted, remove from the oven and allow them to cool slightly. Tear or chop the croissants into bite-sized pieces and set aside.
Step 2: Sauté Vegetables
In a large skillet, heat 2 tablespoons of unsalted butter over medium-low heat. Add the diced onion and minced garlic, and sauté for approximately 5 minutes until the onion becomes soft and translucent. Add the chopped mushrooms and cook for another 5 minutes, until they are tender and plump. Stir in the baby spinach and cook until just wilted, about 2 minutes. Season with a generous pinch of kosher salt and freshly ground black pepper to enhance the flavor. This savory vegetable mixture forms the heart of your breakfast bake, providing a contrast to the richness of the croissants and custard.
Step 3: Assemble Croissant and Vegetable Layers
Prepare a 9×13-inch baking dish by brushing the interior with melted butter to prevent sticking. Combine the toasted croissant pieces with the sautéed vegetable mixture in the baking dish. Toss gently to distribute the vegetables evenly among the croissants. This layering ensures that each bite has a balanced combination of buttery croissant and flavorful vegetables.
Step 4: Prepare the Egg Custard
In a large mixing bowl, whisk together 8 large eggs, 2 ½ cups milk, and 1 cup heavy cream until fully blended. Add a big pinch of salt and freshly ground black pepper. Stir in 1 cup of freshly grated gruyere cheese and, if desired, a handful of fresh chopped parsley and chives. This custard mixture is rich and creamy, soaking into the croissants and vegetables to create a soft, luscious texture.
Step 5: Combine Custard with Croissants and Vegetables
Pour the egg custard mixture evenly over the croissant and vegetable mixture in the baking dish. Press down gently on any croissant pieces that float above the liquid to ensure they are fully soaked in the custard. This ensures that the croissants absorb the rich custard while maintaining their crisp edges. Cover the baking dish tightly with plastic wrap.
Step 6: Refrigerate Overnight
Place the covered baking dish in the refrigerator for at least 8 hours, or overnight. This step allows the croissants to fully absorb the custard, resulting in a bake that is tender, creamy, and flavorful throughout. While some recipes suggest a minimum of 4-6 hours, allowing the dish to sit overnight gives the best results for texture and depth of flavor.
Step 7: Preheat Oven and Prepare for Baking
On the morning you plan to serve, remove the dish from the refrigerator 30 minutes before baking to let it come to room temperature. Preheat your oven to 350°F (175°C). Remove the plastic wrap from the baking dish. Sprinkle the remaining grated gruyere cheese evenly over the top of the custard-soaked croissants for a golden, cheesy finish.
Step 8: Bake the Breakfast Casserole
Bake uncovered in the preheated oven for 45 minutes. The top should be golden brown, and the custard should be set in the center but still slightly soft for a creamy texture. Sprinkle additional parmesan cheese and fresh chopped parsley over the top just before serving for added flavor and visual appeal.
Step 9: Serve and Enjoy
This Overnight Croissant Breakfast Bake is rich, savory, and satisfying. Serve it warm directly from the oven, accompanied by fresh fruit, a light salad, or a cup of freshly brewed coffee or tea. A little goes a long way, as each portion is hearty and flavorful. This breakfast is ideal for special occasions, holiday mornings, or a weekend treat that feels indulgent yet comforting.
Tips for the Perfect Overnight Croissant Breakfast Bake
- Use fresh, high-quality croissants for maximum buttery flavor and flakiness.
- Toasting the croissants is crucial—it adds caramelized notes and prevents sogginess.
- Don’t skimp on custard—the generous amount of eggs, milk, and cream makes the bake rich and creamy.
- Customize your vegetables—spinach, mushrooms, onions, bell peppers, or zucchini all work beautifully.
- Add herbs—parsley, chives, or tarragon add freshness and complexity.
- Prepare the night before—overnight refrigeration allows flavors to meld and ensures a tender, custardy texture.
Storage
- Refrigerator: Cover leftovers tightly and store for up to 3 days. Reheat in a 350°F oven until warmed through.
- Freezer: Portions can be frozen before baking. Thaw overnight in the refrigerator and bake as directed.
