Overnight Breakfast Casserole

This make-ahead croissant breakfast bake turns flaky croissants into a mouthwatering morning dish you can fix the night before. As someone who often hosts family gatherings, I've come to rely on this creation as my go-to trick for hanging out with my guests instead of being trapped cooking all morning.

I first whipped up this bake when hosting my in-laws during a holiday visit. The way their faces lit up after their first taste told me right away that we'd found our new family tradition for special breakfasts.

What You'll Need

• Six large croissants: Ripped into chunks forms the buttery foundation with perfect pockets for soaking up the egg mix
• One pound breakfast sausage: Gives rich protein and flavor, try getting it with sage for extra tastiness
• Two cups shredded cheddar cheese: Makes those delicious stringy pulls, pick mild or sharp depending what you like
• Six large eggs: Creates the custardy base that holds everything together, let them warm up first for best results
• Two cups milk: Adds the perfect smooth texture, full-fat works best here
• Dry mustard: Adds a slight zip that cuts through the richness
• Salt and pepper: Pulls all the flavors together nicely

How To Make It

Get Your Dish Ready:

Coat your 9×13 baking dish with butter, making sure to cover all sides. Cut or tear croissants into roughly 2 inch chunks and spread them out in the dish. Don't pack them too tight—leave some breathing room so the egg mixture can soak in properly.

Layer In The Good Stuff:

Cook your breakfast sausage in a pan until it's nicely browned, breaking it up as it cooks. Drain off the extra grease with paper towels, then sprinkle it evenly over your croissant pieces. Top everything with an even layer of cheese, making sure every serving will get plenty.

Mix Up The Liquid:

In a big bowl, beat the eggs until they're frothy, about half a minute of good whisking. Pour in the milk, add the dry mustard, salt, and pepper, then keep whisking until everything's mixed well. Watch out for mustard clumps—keep going until your mixture looks smooth and consistent.

Put It All Together:

Gently pour the egg mixture all over your dish, trying to cover everything evenly. Use a spoon to lightly push down on the croissant pieces so they start soaking up the liquid. They'll float at first but don't worry—they'll soak up the mixture as they sit.

Let It Rest:

Cover everything tightly with plastic wrap and stick it in the fridge for at least 2 hours, but leaving it overnight works even better. This waiting step is super important—it lets the croissants soak up all the egg mixture, giving you a pudding-like texture instead of dry bread with eggs.

Bake It Up:

Heat your oven to 350°F and take the casserole out of the fridge while the oven warms up. Bake it uncovered for 40 to 45 minutes until it's golden brown on top and firm in the middle. It should wobble slightly but not look wet or runny.

Dig In:

Let it cool for 5 to 10 minutes before cutting into it. This quick rest makes for cleaner slices and lets the flavors settle. Serve it while it's still warm when the cheese is perfectly melty.

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My favorite thing about this breakfast bake is how the croissant edges sticking out get crispy and golden while the inside stays soft and custardy. This mix of textures reminds me of my grandma's bread pudding, though she'd never have thought to use fancy croissants.

Tasty Twists

This breakfast dish is super flexible and works with whatever you've got in your fridge. Try using crispy bacon or diced ham instead of sausage. If you don't eat meat, throw in some cooked mushrooms, spinach, and colorful peppers. Switch up the cheese with Swiss, Gruyère, or spicy pepper jack depending on what flavors you like. For a hint of sweetness, toss in some chopped apple or a handful of fresh berries right before you pop it in the oven.

What To Serve With It

This bake tastes amazing by itself, but I love creating a whole spread around it. A light green salad with tangy dressing balances out the richness perfectly. Some fresh fruit, especially oranges or berries, adds a nice contrast to the savory flavors. When we're celebrating something special, I'll set up mimosas or a DIY Bloody Mary bar next to a pot of coffee. I also put out a small bowl of maple syrup so folks can add a drizzle of sweetness if they want.

Keeping Leftovers

One of the best things about this dish is how good it tastes the next day. Just put any extra portions in a sealed container in the fridge and they'll stay tasty for up to three days. When you want a single serving, pop it in the microwave for 1 to 2 minutes until it's hot. If you prefer a crispier texture, warm it up in the oven at 325°F for about 15 minutes. This bake freezes really well too. Once it's cooled, cut leftovers into single portions, wrap them tightly in plastic, and freeze for up to two months. Just let them thaw in the fridge overnight before warming them up.

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Frequently Asked Questions

→ Can croissants be swapped for a different bread?

Totally! Brioche, challah, or even regular sandwich bread works just fine.

→ What can I use instead of sausage?

No problem! Swap it with bacon, ham, or go veggie with plant-based alternatives—or leave it out.

→ Can I freeze the dish before baking?

Yes, assemble it ahead of time and freeze before cooking. Let it thaw in the fridge overnight for best results before baking.

→ How do I make sure the bread absorbs the eggs?

Use a spatula to gently press down the layers once you've poured the egg mixture over.

→ What veggies go well in this casserole?

Throw in diced peppers, mushrooms, onions, or even spinach for extra flavor and nutrition.