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Some mornings in my kitchen feel like a small holiday, even when the calendar insists it is just Sunday. Coffee is brewing, the house is quiet, and all I want is something buttery, warm, and worthy of a second cup.
This croissant breakfast casserole is my go-to for those cozy brunches, especially when I want a make-ahead breakfast that still feels restaurant-level. The trick is professional custard logic, so the center stays tender, never soggy, and the top bakes up crisp and shatteringly golden.
Why You’ll Love This Recipe
Brunch-host freedom: I love that it can be assembled ahead, so you are not whisking eggs while guests are arriving, you are pouring mimosas and actually enjoying the table.
The secret French-style infusion: Whisking a beurre noisette into the dairy, plus a pinch of freshly grated nutmeg, gives the egg custard a deep, toasty perfume that tastes like it came from a bistro.
Cheese that tastes grown-up: Gruyere cheese brings that nutty melt, and white Cheddar adds a sharp edge, so every bite feels rich but not flat.
Texture that stays exciting: Croissants soak up custard like a dream, but the exposed tips toast and crackle, giving you that perfect contrast between creamy and crisp.
Ingredients and Substitutions
These are simple brunch staples, but each one has a job, from crisp slab bacon to the rich milk and cream that keeps the custard lush and soufflé-like.
Ingredients
- 8 large croissants ripped into 2-3-inch pieces
- 8 oz slab bacon sliced into batons about ¼-inch thick
- 1 cup Gruyere cheese shredded
- 1/2 cup white Cheddar cheese shredded
- 8 large eggs
- 2 cups whole milk
- 1 cup heavy cream
- 2 Tbsp finely chopped sage
- 2 tsp Dijon mustard
- 1 tsp Kosher salt
- 1/4 tsp freshly ground black pepper
Ingredient Notes & Substitutions
Croissants: Day-old or slightly stale croissants are the whole game here, they drink in egg custard without collapsing into pudding. I keep bakery croissants on the counter overnight, then tear them so you get craggy edges that toast beautifully.
Cheese Selection: Gruyere has that alpine, nutty melt that feels made for brunch, while white Cheddar brings a clean, tangy bite. If you need a swap, a good Swiss-style cheese stands in nicely for Gruyere, and a sharp Cheddar keeps the balance.
The Dairy Ratio: The combination of whole milk and heavy cream is what gives you that tender, almost soufflé-like set, instead of a watery scramble in a pan. Half-and-half can work in a pinch, but you lose some of that lush custard body.
Sage and Dijon mustard: Fresh sage makes the whole bake smell like a holiday breakfast, earthy and cozy. Dijon mustard is subtle, it brightens the richness and plays especially well with Gruyere cheese.
Food waste bonus: I love using “past its prime” pastry here, because stale bread can be repurposed in smart, tasty ways, and the EPA even highlights this idea in their guidance on stale bread can be repurposed.
How to make croissant breakfast casserole
Brown butter infusion and oven prep
- Heat your oven to 350F and get a 9×13 baking dish ready with nonstick cook spray, I want the corners protected so the custard releases cleanly.
- For the chef’s step, brown 2 to 3 tablespoons of butter in a small pan until it smells nutty and the milk solids turn amber, then whisk it into the whole milk and heavy cream while still warm, adding a pinch of freshly grated nutmeg if you have it.
Crisp the bacon and build the base
- Set a skillet over medium heat, then add the slab bacon batons once the pan feels hot, not smoking. Stir often for about 4 to 5 minutes, until the fat renders and the bacon looks bronzed and crisp at the edges.
- Scoop the bacon out with a slotted spoon so the extra fat stays behind, then spread the bacon in the bottom of your prepared baking dish, this keeps the meat from overbrowning on top later.
Layer, pour, and finish with a golden bake
- Stir the Gruyere cheese and white Cheddar together, then scatter about half over the bacon. Tuck the croissant pieces on top without packing them tight, I like leaving a few tips pointing upward so they catch heat and turn extra crunchy.
- In a large bowl, whisk the eggs until the yolks and whites are fully blended, then whisk in the infused milk and cream, sage, Dijon mustard, Kosher salt, and black pepper. Pour slowly over the croissants, letting the custard seep into the layers, then finish with the remaining cheese.
- Bake for 40 to 45 minutes, until the top is golden brown and the cheese looks crisped and lacy. At 30 minutes, peek in, and if the croissants are browning too fast, lay a sheet of aluminum foil loosely over the top.
- Let it cool for 5 to 10 minutes before slicing, the center will set as it rests, and the smell will turn from “eggy” to warmly toasted and savory.
Secrets for a Flawless Casserole
The temperature target: The safest, most tender set is when the center reaches 160°F (71°C). I check in the middle, not the edge, because edges always cook faster.
Handling different croissant sizes: For mini croissants, keep the 2 to 3-inch tearing rule, and aim for the same loose, airy layering in the 9×13 baking dish. For jumbo bakery croissants, tear a little smaller so custard can flow between pieces.
Avoiding the “weeping” effect: Puddling usually comes from underbaking or using lower-fat dairy, because the egg proteins do not set firmly enough. The science is similar to custardy eggs in any form, and I explain it the same way I do when talking about mastering egg custard at home.
Freezing wisdom: Unbaked casserole freezes best when wrapped airtight, then thawed in the fridge overnight before baking at 350F. Baked leftovers can also be frozen in portions, but the top loses a bit of croissant crisp, so I always reheat in the oven to bring it back.
Pro Tips & Troubleshooting
Pro Tips
- Keep the bacon under the croissants, it protects it from scorching.
- A quick pre-toast helps, spread croissant pieces on a sheet and toast 5 minutes at 425°F, then assemble as written.
- A blender makes the custard ultra-smooth, with no streaks of egg white.
- Leave space between croissant pieces, custard needs channels to circulate.
- If the top browns early, foil at the 30-minute mark prevents bitterness.
Common Mistakes to Avoid
- Overbaking, it turns the custard spongy and a little dry.
- Using low-fat dairy, the casserole can bake up watery and thin.
- Adding high-moisture vegetables raw, sauté and drain first.
- Packing the croissants too tightly, which blocks an airy rise.
Serving & Storage
Serving Ideas
I like serving this rich bake with something bright and acidic, a citrusy fruit salad or even pineapple and berries, because it cuts through the butter and cheese. A cool dollop of crème fraîche on top looks elegant, and tastes even better once it starts melting.
If you want to lean into the savory side, a simple roasted vegetable plate works well, and something like a bacon side dish feels extra cozy for a holiday breakfast spread. Finish with freshly sliced chives right before bringing it to the table, the green bite wakes everything up.
Storage & Reheating
Refrigerate leftovers covered, and aim to eat them within 3 to 4 days for best texture. For reheating, I use a 350F oven until warmed through, the microwave makes the croissants go soft and a little rubbery.
If you are reheating a larger portion, cover with foil for the first part so it heats evenly, then uncover at the end to re-crisp the top. Let it sit for a couple minutes before eating, the custard firms back up as it cools slightly.
Buttery Croissant Breakfast Casserole
Equipment
- 9×13 Baking Dish
- Small pan
- Skillet
- large bowl
- Whisk
Ingredients
- 8 large croissants ripped into 2-3-inch pieces
- 8 oz slab bacon sliced into batons about ¼-inch thick
- 1 cup Gruyere cheese shredded
- 1/2 cup white Cheddar cheese shredded
- 8 large eggs
- 2 cups whole milk
- 1 cup heavy cream
- 2 Tbsp finely chopped sage
- 2 tsp Dijon mustard
- 1 tsp Kosher salt
- 1/4 tsp freshly ground black pepper
Instructions
Brown butter infusion and oven prep
- Preheat your oven to 350F and coat a 9×13 baking dish with nonstick cooking spray to ensure the custard releases cleanly from the corners.
- Brown 2 to 3 tablespoons of butter in a small pan until it becomes fragrant and the milk solids turn amber. Whisk the warm brown butter into the whole milk and heavy cream, adding a pinch of freshly grated nutmeg if desired.
Crisp the bacon and build the base
- Place a skillet over medium heat and add the slab bacon batons. Stir frequently for 4 to 5 minutes until the fat renders and the bacon is bronzed and crisp.
- Using a slotted spoon, remove the bacon from the skillet and spread it evenly across the bottom of the prepared baking dish.
Layer, pour, and finish with a golden bake
- Mix the Gruyere and white Cheddar together. Scatter half of the cheese over the bacon, then tuck the croissant pieces on top loosely, ensuring some tips point upward for extra crunch.
- In a large bowl, whisk the eggs until fully combined. Mix in the infused milk and cream mixture, sage, Dijon mustard, salt, and pepper. Slowly pour the custard over the croissants and top with the remaining cheese.
- Bake for 40 to 45 minutes until the top is golden brown and the cheese is crisp. If the croissants brown too quickly, cover loosely with foil after 30 minutes.
- Remove from the oven and let the casserole cool for 5 to 10 minutes to allow the custard center to set properly before slicing.
Notes
Nutrition
The Verdict on Savory Croissant Bakes
What makes this one special is the flavor journey, from nutty brown butter in the custard to the crisp, cheesy top and that salty bacon underneath. It eats like brunch at your favorite spot, but it is calm, familiar, and made in your own kitchen.
Once you have this savory version in your back pocket, a sweet brunch feels just as doable, and my pistachio croissant recipe is the kind of treat I bring out when I want a little pastry-shop magic at home.
