irresistible Overnight Croissant Breakfast Casserole

If you’re searching for the ultimate make-ahead breakfast, look no further than this irresistible Overnight Croissant Breakfast Casserole. It’s what brunch dreams are made of: fluffy eggs, savory sausage, melty cheese, and buttery croissant pieces baked together to golden perfection. The best part? All the prep happens the night before, so you can simply wake up, pop it in the oven, and let the magic happen while you sip your coffee. This crowd-pleasing recipe is delightfully easy—just remember to grease a 9×13-inch baking dish, and you’re on your way to breakfast bliss!

Ingredients You’ll Need

What makes this casserole so special is how it brings together humble, everyday ingredients that just sing when combined. Each element plays a crucial part, from the rich croissants which soak up the flavors, to the gooey cheese that binds it all together. Here’s what you’ll need and why you’ll love each ingredient:

• Croissants: Use six large croissants, cut into pieces—their flaky, buttery texture is the star of the dish and absorbs the custard beautifully.
• Breakfast Sausage: One pound, cooked and crumbled, adds a savory, satisfying bite that pairs perfectly with the richness of the croissants.
• Cheddar Cheese: Two cups, shredded, for creamy melt and tangy flavor—feel free to mix in a little mozzarella or Swiss if you’re feeling adventurous!
• Eggs: Six large eggs act as the binder, creating that classic breakfast casserole texture.
• Milk: Two cups help create a luscious, custardy base—whole or 2% work best, but any variety will do.
• Dry Mustard: One teaspoon rounds out the flavors with a subtle kick and depth in the backbone of the dish.
• Salt: A half teaspoon keeps everything seasoned and flavorful without overdoing it.
• Black Pepper: A quarter teaspoon, just enough to brighten up the casserole and wake up those taste buds.

How to Make Grease a 9×13-inch baking dish

Step 1: Prepare the Dish—Grease a 9×13-inch Baking Dish

Before anything else, grease a 9×13-inch baking dish generously. This simple step ensures every golden slice comes out perfectly, leaving nothing stuck behind. It also means easier clean-up later, so you can truly relax after breakfast. Arrange your croissant pieces evenly throughout the pan, making sure the base is well covered.

Step 2: Build the Layers

Sprinkle your cooked and crumbled breakfast sausage evenly over the croissant pieces. Be gentle—think of it as tucking bits of savory goodness into every nook and cranny. Next, scatter the shredded cheddar cheese so there’s a little meltiness in every bite. At this point, the colors and aromas are already so inviting, you know breakfast is going to be special.

Step 3: Whisk Up the Egg Mixture

In a big mixing bowl, whisk together the eggs, milk, dry mustard, salt, and black pepper until perfectly combined. Take your time here—the more uniform your mixture, the fluffier and creamier your casserole will be. This custard soaks into the croissant chunks, flavoring every single layer.

Step 4: Assemble and Soak

Now, pour the egg mixture slowly and evenly over the croissant, sausage, and cheese layers. Press down very gently with a spatula or the back of a spoon, just to help everything settle in and ensure the croissants soak up that glorious custard. Cover the pan tightly with plastic wrap and refrigerate overnight (or at least a couple of hours, if you’re short on time). This is when all the flavors mingle and magic happens.

Step 5: Bake to Perfection

Preheat your oven to 350°F (175°C). Remove your casserole from the fridge and let it sit on the countertop while the oven heats up—this makes for more even baking. Remove the plastic, then bake, uncovered, for 40-45 minutes. You’ll know it’s ready when the top is golden brown and the custard is set. Let it cool for a few minutes before slicing—you want those layers to settle just enough so every serving is picture-perfect.

How to Serve Grease a 9×13-inch baking dish

Garnishes

Garnishing is about adding that little extra flourish. Try a sprinkle of fresh chopped chives or Italian parsley for a pop of green and a bit of freshness. For a hint of heat, offer some hot sauce or red pepper flakes on the side. Even a dollop of sour cream can add a tangy twist that’s surprisingly delicious.

Side Dishes

This casserole shines as the centerpiece, but it loves good company! Serve it with a refreshing fruit salad—think juicy orange slices and berries—or some crispy roasted potatoes. If you’re feeling fancy, sautéed greens or a simple green salad will balance out the richness perfectly.

Creative Ways to Present

For brunch parties, try baking the casserole in individual ramekins (just remember to grease a 9×13-inch baking dish for larger gatherings). Or, cut the finished casserole into neat squares and stack them on a lovely platter, garnished with microgreens. If you’re serving a crowd, set up a “build-your-own” breakfast bar with plenty of toppings and let everyone customize their plate.

Make Ahead and Storage

Storing Leftovers

Leftovers will keep beautifully! Just transfer any cooled pieces to an airtight container and refrigerate for up to three days. Be sure to grease a 9×13-inch baking dish if you’re transferring portions back to reheat in the oven, to prevent sticking and preserve all those delicious layers.

Freezing

This casserole is also very freezer-friendly. After baking and cooling, cut it into portions, wrap them tightly in foil, and freeze for up to two months. To reheat from frozen, grease a 9×13-inch baking dish, arrange uncrowded pieces, and warm in a low oven until heated through.

Reheating

The best method for reheating is to use the oven so you maintain that lovely golden top and moist interior. Simply grease a 9×13-inch baking dish, add the slices, and bake at 325°F until heated through—usually about 20 minutes. For a quick fix, the microwave works too, just use a lower power setting to keep the eggs tender.

FAQs

Can I use store-bought croissants or do they need to be fresh?

Absolutely! Store-bought croissants work perfectly for this casserole. In fact, day-old croissants are ideal since they hold up better after soaking in the custard overnight, giving you that perfect, non-soggy texture.

What can I substitute for sausage if I want a vegetarian version?

There are so many delicious options! You can sauté mushrooms, spinach, and bell peppers for a veggie-packed twist, or use your favorite plant-based sausage alternative. Just make sure to season well for maximum flavor.

Can I assemble and bake this the same day if I forget to refrigerate overnight?

Yes! While overnight soaking gives you the very best flavor and texture, letting it rest for at least two hours in the fridge will still produce great results. Be sure the croissants have some time to soak up the custard for an even bake.

How do I know when the casserole is fully cooked?

Your casserole is ready when the top is deeply golden, the center no longer jiggles, and a knife inserted comes out clean. If you see a runny middle, give it a few more minutes in the oven—every oven is a little different.

Can I bake this casserole in a different sized dish?

You can, just adjust the cooking time as needed. For smaller or deeper pans, you may need a bit more time. For larger pans, check early to avoid overcooking. Whenever you switch pans, don’t forget to grease a 9×13-inch baking dish or whatever size you’re using for best results.

Final Thoughts

This Overnight Croissant Breakfast Casserole brings together comfort, ease, and unforgettable flavor, making it a true favorite in my kitchen. Whether you’re planning ahead for guests or simply treating yourself, you’ll love how easy it is—just grease a 9×13-inch baking dish and let your oven do the rest! Give it a try and make breakfast the highlight of your day.

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