Grease a 9×13-inch baking dish Recipe

This overnight croissant breakfast casserole is the ultimate answer to cozy, make-ahead brunches with family or friends. But before you whisk a single egg, remember this life-changing tip: always Grease a 9×13-inch baking dish. With buttery croissants, savory sausage, melty cheddar, and a perfectly seasoned egg custard, this casserole is irresistibly rich and satisfying. Whether you’re prepping for a holiday gathering or just want to make mornings easier, each bite delivers that magic combination of crisp edges and pillowy-soft, flavor-packed center. Trust me—once this enters your breakfast rotation, there’s no looking back!

Ingredients You’ll Need

Every item in this casserole is chosen for a reason, and together, the few simple ingredients create a dish that’s far greater than the sum of its parts. Each one layers in flavor, texture, or color, and when you Grease a 9×13-inch baking dish and bake it all together, the results are pure breakfast heaven.

• Croissants: Day-old or fresh, croissants bring buttery flakiness and absorb the custard beautifully.
• Breakfast sausage: Adds bold savory flavor and heartiness; feel free to use spicy or mild, depending on your crowd.
• Shredded cheddar cheese: Melts deliciously for gooey, cheesy pockets throughout the casserole.
• Large eggs: The backbone of your custard, giving the casserole its creamy structure.
• Milk: Keeps the casserole moist and luscious; whole milk gives extra richness but low-fat works too.
• Dry mustard: Enhances flavor with a gentle tang—just enough to balance out the richness.
• Salt: Essential for seasoning the custard base and brightening every bite.
• Black pepper: Adds a soft background warmth that ties in with the sausage and cheese.

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

Step 1: Grease a 9×13-inch baking dish

Start by generously Greasing a 9×13-inch baking dish with butter or nonstick spray. This step is crucial—not only does it prevent sticking, but it also helps develop those lovely golden-brown edges that everyone fights over. Take a moment to get into all the corners to make sure you can serve up every last scrap with ease.

Step 2: Layer the Croissants

Scatter the croissant pieces in an even layer across the bottom of your greased dish. If your croissants are a day old, even better—they’ll soak up the custard while holding their shape. Fluff them up a bit for the perfect base, creating nooks to trap all the savory goodness to come.

Step 3: Add Sausage and Cheese

Next, sprinkle the cooked, crumbled breakfast sausage evenly over the croissants. Follow with a generous shower of shredded cheddar cheese, making sure to cover every surface. This layering ensures each bite is loaded with flavor and stretches that cheesy goodness from corner to corner.

Step 4: Make the Egg Mixture

In a large bowl, whisk together the eggs, milk, dry mustard, salt, and black pepper thoroughly. You want the eggs completely incorporated and the spices evenly distributed. This sumptuous custard will soak into the croissants, transforming everything into a creamy, savory bread pudding.

Step 5: Assemble the Casserole

Carefully pour the egg mixture over the layers in your baking dish. Take a spatula or the back of a spoon and gently press the croissant pieces down, encouraging them to soak up every last drop. This helps ensure a luxuriously moist center after baking.

Step 6: Refrigerate Overnight

Now, simply cover the casserole tightly with plastic wrap and pop it in the fridge. Letting it rest overnight (or at least 2 hours) is the magic step: the flavors meld, and the croissants absorb the custard, resulting in a perfectly set, deeply flavorful breakfast the next day.

Step 7: Bake to Perfection

Preheat your oven to 350°F (175°C). Remove the casserole from the refrigerator, letting it stand at room temperature while the oven heats, which helps it bake evenly. Bake, uncovered, for 40-45 minutes, until the top is gloriously golden and the custard is set but still moist in the center. Let it cool briefly before slicing, so those layers stay intact.

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

Garnishes

A classic casserole like this deserves a little flourish! Once baked, sprinkle with fresh chives or parsley for a pop of color and a fresh, herbal note that brightens up the dish. If you’re looking for more indulgence, a dollop of sour cream or a drizzle of hot sauce takes things up a notch.

Side Dishes

This casserole is deeply satisfying on its own, but it pairs beautifully with simple side salads of baby greens, fresh fruit, or crispy hash browns. The lightness of fruit or a zippy salad balances the rich, savory flavors and adds some lovely contrast to your breakfast spread.

Creative Ways to Present

If you want to serve Grease a 9×13-inch baking dish at a special brunch, try baking and slicing it into neat squares for a buffet. Or, for a fun twist, use small ramekins or muffin tins (just remember to Grease a 9×13-inch baking dish or your chosen vessel) for individual servings—guests will love those extra crispy edges!

Make Ahead and Storage

Storing Leftovers

If you’re lucky enough to have leftovers, let the casserole cool to room temperature, then cover your baking dish tightly or transfer to an airtight container. Store in the refrigerator for up to 3 days; the flavors only deepen as it rests.

Freezing

This casserole freezes like a dream! After baking and cooling, slice into portions and wrap tightly in plastic wrap and foil, or place in freezer-safe containers. Frozen portions will keep for up to two months; just remember to label your packages for easy breakfast planning.

Reheating

To reheat, thaw overnight in the refrigerator if frozen. For best results, cover with foil and warm in a 350°F oven until heated through. Individual slices can also be microwaved for quick breakfasts on busy mornings—don’t forget an extra sprinkle of cheese if you’re feeling indulgent!

FAQs

Can I substitute the croissants with another bread?

While croissants give a buttery, flaky texture, you can use brioche, challah, or even sturdy sandwich bread in a pinch. Just ensure your bread isn’t too soft, so it holds up well to the custard!

What type of sausage works best?

Any breakfast sausage you love will do, from pork to turkey or even plant-based alternatives. For a spicier twist, try hot Italian or chorizo—but always cook and crumble it before adding to the casserole.

Why do I need to Grease a 9×13-inch baking dish?

Greasing the dish ensures easy cleanup and prevents those golden, crispy edges from sticking—plus, it helps your casserole unmold like a dream, with tidy slices every time.

Can I assemble the casserole earlier than overnight?

Absolutely! While an overnight soak yields the richest flavor and texture, even two hours in the fridge lets the croissants absorb that luscious custard and bakes up beautifully.

How do I know when the casserole is done baking?

Look for a golden top and gently jiggle the dish—the center should be set but slightly soft. Insert a knife in the center; if it comes out clean and steaming, your casserole is ready to enjoy!

Final Thoughts

If you’re searching for a no-fuss, crowd-pleasing breakfast that feels both indulgent and comforting, you can’t go wrong with this overnight croissant breakfast casserole. Just remember the cardinal step: always Grease a 9×13-inch baking dish! Give it a try for your next gathering or lazy weekend morning, and get ready for rave reviews from every bite.

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