Introduction

This Overnight Croissant Breakfast Casserole is a comforting and delicious way to start your morning. Combining buttery croissants, savory sausage, and a rich cheese and egg mixture, it’s perfect for busy weekends or special brunches. Make it the night before and wake up to a warm, custardy delight.

A white ceramic baking dish filled with layers of golden brown puff pastry rolls arranged side by side, each roll showing distinct flaky layers with a crispy, slightly shiny top. Inside the rolls, a creamy white cheese mixture and small bits of browned filling are visible, with some cheese melted and slightly browned on the surface between the rolls. The texture looks soft and fluffy inside with a crunchy outer layer. The dish sits on a white marbled texture surface. Photo taken with an iphone --ar 4:5 --v 7

Ingredients

1 tbsp olive oil
1 small onion, peeled and chopped
1 lb breakfast sausage (mild or spicy to taste)
4 large butter croissants (or 8 smaller croissants)
1 cup shredded cheddar cheese (or your favorite cheese blend)
6 large eggs
½ cup heavy whipping cream
3 cups whole milk (divided)
½ tsp dry mustard powder
½ tsp salt (plus more for gravy)
½ tsp black pepper (plus more for gravy)
¼ tsp paprika
¼ tsp garlic powder
2 tbsp butter
3 tbsp all-purpose flour (or gluten-free flour)

Instructions

Step 1: Heat olive oil in a large skillet over medium heat. Add chopped onion and sauté until soft and translucent, about 5-7 minutes. Add crumbled breakfast sausage and cook until browned and fully cooked, roughly 7-10 minutes. Drain excess fat, reserving some for the gravy. Set sausage mixture aside to cool.
Step 2: Tear croissants into bite-sized pieces. In a large bowl, combine croissants, sausage mixture, and half of the shredded cheese. Toss gently to mix.
Step 3: In another bowl, whisk together eggs, heavy cream, ½ cup milk, dry mustard, salt, pepper, paprika, and garlic powder until smooth. Pour this egg mixture evenly over the croissant mixture, pressing down slightly so croissants absorb the liquid.
Step 4: Cover the dish and refrigerate overnight. If short on time, refrigerate for at least 2 hours to allow flavors to meld and croissants to soak up the egg.
Step 5: Preheat oven to 350°F (175°C). Remove casserole from fridge and bake uncovered for 35-45 minutes, until golden brown and set. For a crispier top, broil 2-3 minutes at the end.
Step 6: While baking, make the gravy. Melt butter in a saucepan over medium heat, stir in reserved sausage fat until smooth. Add flour, stirring constantly for 1 minute to form a roux. Gradually whisk in remaining 2½ cups milk and cook until thickened, about 5 minutes. Season with salt and pepper to taste.
Step 7: Let casserole cool a few minutes after baking. Serve warm with generous spoonfuls of sausage gravy on top or on the side.

Tips & Variations

Substitute croissants with gluten-free bread or pastry and use gluten-free flour for the gravy to make this dish gluten-free.
Try different cheeses like Monterey Jack, Gruyère, or sharp white cheddar to vary the flavor.
For a vegetarian version, replace sausage with sautéed vegetables such as mushrooms, spinach, or bell peppers.
Use almond or coconut milk and dairy-free cheese to create a dairy-free casserole.

Storage

Store leftovers covered in the refrigerator for up to 3 days. Reheat in the oven at 350°F (175°C) until warmed through to maintain the casserole’s texture. Avoid microwaving if possible to prevent sogginess.

How to Serve

The image shows a white ceramic baking dish filled with 16 golden brown puff pastry parcels arranged in 4 rows of 4. Each piece has a shiny, crisp, layered top with browned spots and visible flaky layers, puffing upward. Inside, the filling is soft and creamy white with some bits of cooked, browned sausage visible in the middle of the open piece. The dish sits on a white marbled textured surface with a blurred background. Photo taken with an iphone --ar 4:5 --v 7

Serve this delicious recipe with your favorite sides.

FAQs

Can I prepare the casserole without croissants?

Yes, you can use other bread like brioche or gluten-free bread if you prefer. Croissants add a rich, buttery flavor, but substitute breads work well too.

How long can I refrigerate the casserole before baking?

The casserole is best refrigerated overnight or for at least 2 hours. This allows the croissants to fully absorb the egg mixture and develop the best texture and flavor.