Croque Monsieur Breakfast Casserole Recipe (Make-Ahead)

Name: This Easy Make-Ahead Breakfast Casserole Tastes Like a French Bistro
Prep time: 15 min
Cook time: 50 min
Total time: 185 min
Ingredients: 1 tablespoon unsalted butter, softened, for greasing the dish; 1 loaf rustic Italian, challah, or brioche bread, cut into 1-inch cubes (about 8 cups); 8 ounces deli ham, roughly chopped; 2 cups shredded Gruyère or Swiss cheese, divided; 1/2 cup grated parmesan cheese; 6 large eggs; 2 cups whole milk; 1 cup heavy cream; 1 tablespoon Dijon mustard; 1/2 teaspoon kosher salt; 1/4 teaspoon freshly ground black pepper; 1 pinch ground nutmeg, optional

This casserole brings together smoky ham, melty Gruyère cheese, and tender bread for comforting French flavor inspired by a Croque Monsieur sandwich.
You can assemble it the night before for a stress-free breakfast or brunch.
The recipe makes enough for a crowd, so it is excellent for holiday gatherings.

If a fancy French café sandwich and a cozy breakfast bake had a baby, it would be this Croque Monsieur breakfast casserole. It’s buttery, cheesy, and full of smoky ham—pretty much everything you love about a classic Croque Monsieur, baked into one easy, make-ahead dish.

The first time I made this, my family actually fought over the last piece. Now it’s my go-to for busy holiday mornings. If you serve this, you’ll keep everyone happily full and out of the kitchen while you focus on the big dinner ahead, or just sneak a quiet cup of coffee for yourself.

A baked casserole dish of croque monsieur breakfast casserole featuring layers of toasted bread ham and melted cheese — Simply Recipes / Photo by Alex Huang / Food Styling by Kaitlin Wayne

What Makes This Breakfast Casserole Special

Breakfast casseroles usually start with the same base: eggs, milk, maybe some cheese, and some type of bread. The bread soaks up the custard, baking into a creamy, tender interior with a golden, crisp top.

This version takes inspiration from the French Croque Monsieur sandwich. Big hunks of artisan bread, smoky ham, and melty Gruyère cheese make it rich and satisfying, while Dijon mustard and a touch of nutmeg give it that signature French flavor.

Day-old bread works best here, as it absorbs the custard without falling apart. If you don't happen to have day-old bread lying around, just toss your bread pieces in a 200°F oven for 10 to 30 minutes until slightly dried out. Brioche or challah will give your casserole a buttery texture, but I actually prefer a good rustic artisan loaf with an open crumb so the custard has little places to hide.

If you can, assemble the dish the night before. Letting it rest overnight allows the bread to soak up every last bit of the custard, creating the perfect soft-meets-crispy-meets-cheesy balance once baked. Plus, it makes the morning of your gathering so much simpler—just toss it in the oven and you’re done!

A casserole dish with baked breakfast casserole served with juice and fruit on a table — Simply Recipes / Photo by Alex Huang / Food Styling by Kaitlin Wayne

Easy Tweaks

Once you know the basic formula, you can easily change up the flavors of this recipe. Try any of these twists:

Make it fancy: After baking, top each serving with a rich, cheesy Mornay sauce or a bright Hollandaise sauce.
Make it a Madame Add fried or poached eggs on top of each serving to make it into a Croque Madame.
Make it veggie Replace the ham with sautéed mushrooms, spinach, or roasted red peppers.

Serving Suggestions

This casserole is certainly hearty enough to be a meal all on its own, but simple sides will stretch it to feed a hungry crowd. For breakfast or brunch, serve with fresh fruit or a citrus salad. For lunch, add a green salad with light vinaigrette. Eggs, potatoes (hello, more carbs), and something sweet will fill out the brunch table with enough for everyone!

Dish of baked croque monsieur casserole with cheese and bread visible — Simply Recipes / Photo by Alex Huang / Food Styling by Kaitlin Wayne

Croque Monsieur Breakfast Casserole

Prep Time 15 mins

Cook Time 50 mins

Chilling Time: 2 hrs

Total Time 3 hrs 5 mins

Servings 8 to 10 servings

Yield 1 (9x13-inch) casserole

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1 tablespoon unsalted butter, softened, for greasing the dish
1 loaf rustic Italian, challah, or brioche bread, cut into 1-inch cubes (about 8 cups)
8 ounces deli ham, roughly chopped
2 cups shredded Gruyère or Swiss cheese, divided
1/2 cup grated parmesan cheese
6 large eggs
2 cups whole milk
1 cup heavy cream
1 tablespoon Dijon mustard
1/2 teaspoon kosher salt
1/4 teaspoon freshly ground black pepper
1 pinch ground nutmeg, optional

Assemble the casserole:

Butter a 9x13-inch baking dish. Layer half of the bread cubes in the greased dish, followed by half of the ham and 3/4 cup of the Gruyère. Repeat with the remaining bread, ham, and another 3/4 cup cheese.

Combine the parmesan and the remaining 1/2 cup Gruyère in an airtight container and set aside in the refrigerator for topping the casserole later.
Add the custard:

In a large bowl, whisk together the eggs, milk, cream, Dijon mustard, salt, pepper, and nutmeg, if using, until well combined.

Pour the mixture evenly over the casserole, pressing the bread down slightly so it absorbs the liquid. Cover tightly and refrigerate for at least 2 hours or overnight.
Bake:

When ready to bake, preheat the oven to 350°F. Uncover the casserole and sprinkle the reserved cheeses evenly over the top. Bake until puffed, golden, and set in the center, 45 to 50 minutes. If the top browns too quickly, tent with foil during the last 10 minutes of baking.
Cool and serve:

Let the casserole rest for 10 minutes before slicing. Serve warm.

Store leftovers in an airtight container in the refrigerator for up to 3 days. Reheat in a 350°F oven for 15 to 20 minutes until warmed through, or microwave individual portions until hot.

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Nutrition Facts (per serving)
390	Calories
25g	Fat
21g	Carbs
21g	Protein

Nutrition Facts
Servings: 8 to 10
Amount per serving
Calories	390
% Daily Value*
Total Fat 25g	32%
Saturated Fat 13g	67%
Cholesterol 182mg	61%
Sodium 775mg	34%
Total Carbohydrate 21g	7%
Dietary Fiber 1g	4%
Total Sugars 4g
Protein 21g
Vitamin C 0mg	1%
Calcium 372mg	29%
Iron 2mg	10%
Potassium 304mg	6%
*The % Daily Value (DV) tells you how much a nutrient in a food serving contributes to a daily diet. 2,000 calories a day is used for general nutrition advice.

Nutrition information is calculated using an ingredient database and should be considered an estimate. In cases where multiple ingredient alternatives are given, the first listed is calculated for nutrition. Garnishes and optional ingredients are not included.