Ham and cheese croissant breakfast casserole turns day-old croissants, cooked ham, two cheeses, and a Dijon egg custard into an easy make-ahead brunch. Assemble it before bed, refrigerate overnight, and bake it in the morning for a tender center and crisp golden top.
This savory casserole answers the practical holiday-breakfast problem: it feeds eight without requiring anyone to stand at the stove. Slightly dry croissants absorb the custard more evenly than very fresh ones, and a covered-then-uncovered bake keeps the middle moist while the top browns.
Overnight Ham and Cheese Croissant Breakfast Casserole
Prep: 20 minutes · Chill: 8 hours · Cook: 50 minutes · Total: 9 hours 10 minutes · Yield: 8 servings
Ingredients
- 8 day-old butter croissants, cut into 1 1/2-inch pieces
- 8 ounces fully cooked ham, diced
- 1 1/2 cups shredded Gruyère or Swiss cheese, divided
- 1 cup shredded sharp cheddar cheese, divided
- 8 large eggs
- 2 cups whole milk
- 1/2 cup plain Greek yogurt or sour cream
- 1 tablespoon Dijon mustard
- 1/2 teaspoon garlic powder
- 1/2 teaspoon kosher salt
- 1/4 teaspoon black pepper
- 2 tablespoons chopped fresh chives, plus more for serving
- Nonstick cooking spray or softened butter, for the dish
Directions
- Prepare the dish: Coat a 9-by-13-inch or 3-quart baking dish with cooking spray or butter.
- Layer the filling: Arrange half of the croissant pieces in the dish. Scatter on the ham, 1 cup Gruyère, and 3/4 cup cheddar. Top with the remaining croissants.
- Mix the custard: Whisk the eggs, milk, yogurt, Dijon, garlic powder, salt, pepper, and chives until smooth. Pour evenly over the croissants. Press gently so the top pieces touch the custard without packing them down.
- Chill overnight: Cover and refrigerate for 8 to 12 hours. This gives the croissants time to absorb the custard.
- Prepare to bake: Remove the casserole from the refrigerator for 30 minutes while the oven heats to 350°F.
- Bake safely: Cover with foil and bake for 30 minutes. Uncover, add the remaining 1/2 cup Gruyère and 1/4 cup cheddar, then bake 15 to 20 minutes more. The top should be browned and the center should register 165°F because the egg dish contains ham.
- Rest and serve: Rest for 10 minutes so the custard sets, then sprinkle with extra chives and cut into 8 portions.
Why use day-old croissants?
Fresh, very soft croissants can collapse before the custard sets. Croissants that have rested uncovered for several hours—or overnight—retain distinct buttery layers while still absorbing the egg mixture. If yours are fresh, spread the pieces on a sheet pan and bake at 300°F for 8 to 10 minutes, then cool completely.
Tips for a casserole that is tender, not soggy
- Measure the milk: Extra liquid can leave the center loose.
- Use a roomy dish: A 3-quart or 9-by-13-inch dish gives the custard room to cook evenly.
- Do not skip the counter rest: Thirty minutes takes the chill off the glass dish and helps the center bake at the same pace as the edges.
- Check the center: Temperature is more reliable than color. The casserole is ready at 165°F in its thickest part.
- Rest before slicing: Ten minutes lets the custard finish setting.
Useful variations
- Turkey and Swiss: Replace the ham with fully cooked turkey and use Swiss cheese throughout.
- Cooked sausage: Use 8 ounces of browned, well-drained breakfast sausage.
- Vegetarian: Omit the ham and add 8 ounces of sautéed mushrooms plus 1 cup of wilted, squeezed-dry spinach.
- Cheddar-only: Use 2 1/2 cups sharp cheddar if Gruyère is unavailable.
- French bread: Substitute about 10 cups of day-old bread cubes; the texture will be less rich but still satisfying.
Make-ahead, storage, and reheating
Assemble and refrigerate the unbaked casserole for 8 to 12 hours. After baking, refrigerate leftovers within 2 hours in a covered container and use within 3 to 4 days. Reheat individual portions in the microwave, or cover and warm in a 325°F oven, until the center reaches 165°F. Freeze fully baked, cooled portions for up to 2 months; thaw overnight before reheating.
Frequently asked questions
Can it soak longer than overnight?
Eight to 12 hours gives the best texture. Up to 16 hours is workable, but the top will be softer.
Can I bake it immediately?
Yes, but let it stand at room temperature for 30 minutes after assembly so the croissants absorb some custard. The finished layers will be more distinct and a little less unified.
Why is my breakfast casserole watery?
Common causes are using extra milk, adding wet vegetables, or removing it before the center is fully set. Cook vegetables first, squeeze spinach dry, measure the liquid, and verify 165°F in the center.
Can I halve the recipe?
Halve every ingredient and bake in an 8-inch square dish. Begin checking after 30 minutes, then cook until the center reaches 165°F.
What to serve with it
For a savory make-ahead spread, pair this casserole with our spinach feta breakfast casserole. For another filling option, try the make-ahead sausage egg breakfast casserole. Guests who prefer something sweet may like the overnight apple cinnamon French toast casserole.
Helpful baking dish
MealMadeBright Amazon Associate disclosure: MealMadeBright earns from qualifying purchases. This does not change the price you pay.
A clear Pyrex 3-quart rectangular glass baking dish makes it easy to check browning around the edges and is appropriately sized for this recipe.
Estimated nutrition
Estimated per serving (1/8 casserole): 480 calories, 26 g protein, 27 g carbohydrate, 30 g fat, 1 g fiber, 7 g sugar, and 900 mg sodium. Nutrition is an estimate and varies with croissant size, ham, cheese, and brands used.
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