Baked Croque Monsieur Casserole

Name: Baked Croque Monsieur Casserole
Prep time: 25 min
Cook time: 1 h
Total time: 1 h 25 min
Cuisine: French
Ingredients: 5-6 cups sourdough, brioche or country loaf, 1-2 days old and cut into 2-inch cubes; 1 ½ cups cubed ham; 10 tablespoons salted butter, divided; 1 leek, whites only, cut into half moons; 6 eggs; 1 ¼ cups half-and-half; 2 tablespoons Dijon mustard; 1 ½ teaspoons coarse kosher salt, divided; 1 teaspoon ground black pepper, divided; 3 cups Swiss or Gruyere cheese, grated and divided; 2 tablespoons Parmesan cheese, finely grated; 4 tablespoons flour; 2 cups whole milk; 1/4 teaspoon grated nutmeg; 1 tablespoon chives, chopped

By:

dani

Published:

April 16, 2026

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Baked Croque Monsieur Casserole is a delightful twist on the classic French sandwich, combining layers of rich flavors with a comforting casserole format. It features savory ham, creamy cheese, and buttery bread, all baked together into a golden, bubbling delight. This dish has a wonderful balance of textures, with soft, soaked bread and a crunchy top that makes every bite an experience. It’s perfect for brunch gatherings or a cozy family breakfast, giving you all the comforting flavors of a traditional croque monsieur in an easy-to-serve form.

My first encounter with this casserole was at a charming little café where it was served as part of a brunch spread. The moment I took a bite, I was hooked—who wouldn’t fall in love with that melty cheese and savory ham combination? This recipe brings that beloved dish into your home kitchen, effortlessly feeding a crowd while allowing everyone to indulge in its delicious layers. Honestly, there’s something incredibly satisfying about pulling a golden-brown casserole out of the oven and serving it with a side of rich béchamel sauce. I can’t wait for you to try this baked croque monsieur casserole—your taste buds are in for a treat!

Why You’ll Love This Recipe

Simple & Quick: With just 25 minutes of prep time, this dish is a breeze to assemble.
Irresistible Flavor: The combination of Swiss cheese and ham creates an incredible savory experience.
Eye-Catching Appeal: It’s a showstopper at the breakfast table, perfect for impressing guests!
Flexible Serving: Enjoy it for brunch, lunch, or even dinner—it’s versatile enough for any occasion.
Diet-Friendly Options: You can easily swap out ingredients to fit dietary needs, like using gluten-free bread.

Ingredients You’ll Need

5-6 cups sourdough, brioche, or country loaf: The foundation of your casserole. Use day-old bread for the best texture and absorption.
1 ½ cups cubed ham: Essential for that savory taste. A good quality smoked or honey ham works wonderfully.
10 tablespoons salted butter: Adds richness and helps sauté the leeks. Use unsalted butter if you prefer to control the salt.
1 leek, whites only, cut into half moons: Provides a mild, sweet onion flavor. If leeks aren’t available, yellow onions can be a good substitute.
6 eggs: The binding agent that creates custardy layers throughout the casserole. Use large eggs for consistency.
1 ¼ cups half-and-half: Adds creaminess to the custard mix. If you want to lighten it, you can use whole milk instead.
2 tablespoons Dijon mustard: Adds a tangy depth. Feel free to adjust the amount based on your taste preference.
1 ½ teaspoons coarse kosher salt: Enhances all the flavors. Adjust to liking if you prefer a less salty dish.
1 teaspoon ground black pepper: A must for seasoning. You can also use freshly cracked pepper for extra flavor.
3 cups Swiss or Gruyere cheese, grated: This melty cheese is crucial for that classic flavor and gooey texture.
2 tablespoons Parmesan cheese, finely grated: Topping it off with Parmesan gives a nice nutty finish.
4 tablespoons flour: Used to create a roux for the sauce; it thickens and enhances the overall richness.
2 cups whole milk: Adds creaminess to the sauce. Alternatively, you could use almond milk for a lighter version.
1/4 teaspoon grated nutmeg: A warm spice that rounds out the flavors in your béchamel sauce.
1 tablespoon chives, chopped: A fresh garnish that adds color and a mild oniony flavor.

How to Make Baked Croque Monsieur Casserole

Preheat the oven: Set your oven to 375°F and prepare a 9×13 baking dish with some grease or cooking spray.
Prepare the base: In the baking dish, scatter the 5-6 cups of cubed sourdough, brioche, or country loaf along with the 1 ½ cups of cubed ham. Give them a gentle toss to mix slightly, then set aside.
Sauté the leek: In a small saucepan, melt 1 tablespoon of the butter over medium heat. Add the cut leek and cook until soft, about 3-4 minutes. Distribute the sautéed leeks evenly over the bread and ham mixture.
Make the custard: In a medium mixing bowl, combine 5 tablespoons of melted butter, 6 eggs, 1 ¼ cups of half-and-half, 2 tablespoons of Dijon mustard, 1 teaspoon kosher salt, and ½ teaspoon black pepper. Whisk until blended.
Combine with bread: Pour half of the custard mixture over the bread and ham, tossing gently and pressing down to help the bread absorb it. Repeat with the remaining custard. Then, mix in the 3 cups of grated cheese until evenly distributed.
Bake the casserole: Cover the baking dish with aluminum foil and bake for 25 minutes. Then, remove the foil and bake for another 15 minutes or until it reaches an internal temperature of 160°F. Once done, sprinkle the 2 tablespoons of grated Parmesan on top, returning it to the oven under the broiler for 1-2 minutes until golden brown and crispy on the edges.
Prepare the sauce: While your casserole bakes, melt the remaining 4 tablespoons of butter in a saucepan. Whisk in the 4 tablespoons of flour until it forms a roux. Cook for a minute until slightly browned, then slowly whisk in the 2 cups of whole milk. Stir until thickened and smooth, then remove from heat and add the 1/4 teaspoon of grated nutmeg, remaining 1 ½ teaspoons kosher salt, and 1 teaspoon black pepper.
Serve it up: Spoon the sauce over the baked casserole or serve on the side in a gravy boat. Garnish with the chopped chives for a pop of freshness.

Storing & Reheating

Store any leftovers in an airtight container at room temperature for the first couple of hours, then refrigerate for up to 3 days. You can freeze it for up to 3 months, ensuring it’s well-wrapped. To reheat, cover and warm in the oven at 350°F for about 20 minutes until heated through. Keep in mind that while refrigeration preserves the flavor, it may alter the texture a bit—adding a splash of milk before reheating can help restore creaminess.

Chef’s Helpful Tips

Make sure to cut the bread into uniform cubes for even soaking and baking.
Let the eggs and half-and-half come to room temperature before mixing; this ensures a creamier texture.
Don’t skip the broiling step—this is key to getting that deliciously crunchy top.
If your casserole seems too dry before baking, don’t hesitate to add a splash of milk to ensure all the bread is soaked.
You can prep this casserole the night before; simply assemble and refrigerate until ready to bake the next morning!

Baked Croque Monsieur Casserole is not just a recipe; it’s an experience that brings the warmth and comfort of a French café right to your kitchen. With each layer, you get a little more of that delicious flavor, and the best part is how versatile it is. Whether served for brunch, a casual dinner, or even as a cozy weekend treat, it’s bound to impress anyone at your table. Don’t be afraid to experiment with different cheeses or add your favorite veggies for a personalized touch. Enjoy every bite and feel free to share this delightful dish with friends and family!

Recipe FAQs

Can I make this casserole in advance?

Absolutely! You can prepare the casserole the night before, cover it tightly with foil, and store it in the refrigerator. Just pop it in the oven the next morning and enjoy a hassle-free breakfast.

What can I substitute for ham in this recipe?

If you’re looking for alternatives to ham, try using cooked bacon or turkey. You can also replace it with sautéed vegetables or a plant-based alternative for a lighter, vegetarian casserole.

How do leftovers taste the next day?

Leftovers reheat beautifully! The flavors actually deepen overnight, making the casserole even more delicious. Just ensure to reheat gently to avoid drying it out.

Can I freeze this casserole?

Yes! This casserole freezes well. Just be sure to wrap it tightly once it has cooled completely. When you’re ready to eat, thaw it in the refrigerator overnight before reheating.