Croque Monsieur Casserole

The smell of nutmeg hitting warm butter still takes me back to my tiny Paris apartment kitchen, where I first attempted to recreate the Croque Monsieur I'd fallen in love with at a corner bistro. I made such a mess with flour everywhere, but that first bite of creamy, cheesy perfection was absolutely worth the cleanup. Now I've transformed that sandwich into this casserole, which feeds a crowd without the hassle of individual sandwiches.

I served this at my sister's baby shower last spring, and my aunt who claims to dislike French food went back for thirds. The way the béchamel seeps between the layers while it bakes creates these incredible pockets of creamy goodness that make people pause mid-bite and ask what exactly they're eating.

Ingredients

• 12 slices white sandwich bread, crusts removed: Pulling off the crusts prevents any tough, chewy edges and helps the bread absorb that gorgeous custard evenly
• 2 tbsp unsalted butter, softened: Use real butter here, nothing compares to that authentic French flavor and how it creates those golden edges
• 1 1/2 cups Gruyère cheese, grated: Gruyère melts into that perfect creamy, nutty goodness that defines this dish, though Swiss works in a pinch
• 1 cup whole milk: Whole milk creates the richest custard base for soaking the bread
• 1/2 cup heavy cream: This little luxury makes all the difference in the final texture
• 3 large eggs: These bind everything together into that irresistible French toast-like consistency
• 8 slices cooked ham: Good quality deli ham adds just the right salty note to balance all that creaminess
• 2 tbsp unsalted butter: For the béchamel, which is the absolute heart of this recipe
• 2 tbsp all-purpose flour: This creates the silky smooth sauce base
• 1 1/4 cups whole milk: Warm this before adding to prevent any lumps in your sauce
• 1/4 tsp ground nutmeg: The secret ingredient that makes this taste authentically French

Instructions

Get your oven ready:

Preheat to 375°F and butter a 9x13-inch baking dish thoroughly, getting into all the corners

Make the béchamel:

Melt butter over medium heat, whisk in flour for one minute until it smells nutty, then slowly add warm milk while whisking constantly until thickened, about 3 to 4 minutes

Layer it up:

Butter one side of each bread slice, then arrange half buttered side down in your dish, topping with ham and Gruyère before repeating with remaining bread, ham, and cheese

Whisk together the custard:

Beat eggs with milk, cream, and a pinch of salt until combined, then pour evenly over the entire casserole

Add that creamy finish:

Pour your béchamel sauce over the top and spread it into every corner

Bake until golden:

Bake uncovered for 35 to 40 minutes until puffed up beautifully and bubbling, then let rest for 10 minutes before serving

Save

This became my go-to Christmas morning dish after the year I tried making individual Croque Monsieurs for eight people and spent the entire breakfast party at the stove. Now everyone gets to eat together, and I actually get to enjoy the conversation.

Make It Your Own

I've discovered that adding a thin layer of Dijon mustard between the bread and ham creates this incredible depth of flavor that keeps everyone guessing. For a Croque Madame variation, simply fry up some eggs and place one on top of each serving.

The Wine Question

A crisp Chardonnay cuts through all that rich creaminess beautifully, but if you are serving this for brunch, a dry sparkling cider works just as well. The key is something with enough acid to balance the heavy cheese and béchamel.

Perfect Pairings

A simple arugula salad with lemon vinaigrette provides the perfect fresh contrast to all that richness. I also love serving roasted asparagus on the side when it is in season.

• Keep some extra Gruyère handy to sprinkle over the top if it starts browning too quickly
• A layer of sautéed mushrooms works wonderfully instead of ham for a vegetarian version
• Leftovers reheat surprisingly well in a 350°F oven for about 15 minutes

Save

There is something deeply satisfying about taking such an elegant French classic and making it work for a regular Tuesday night dinner or a lazy weekend brunch. This casserole has become one of those recipes I can make without even looking at the page anymore.

Recipe FAQ

→ Can I assemble this casserole in advance?

Yes, you can assemble the Croque Monsieur Casserole up to 24 hours ahead. Prepare all layers and pour the béchamel and egg mixture over the top. Cover tightly and refrigerate. Before baking, let it sit at room temperature for 30 minutes, then bake as directed, potentially adding 5-10 minutes to the cooking time.

→ What are good substitutes for Gruyère cheese?

If Gruyère isn't available, Swiss cheese is a fantastic substitute as it has a similar nutty flavor and melting quality. Other options include Emmental, Comté, or even a good quality sharp white cheddar for a slightly different, but still delicious, flavor profile.

→ How can I make this dish vegetarian?

To make it vegetarian, simply omit the ham. You can replace it with sautéed mushrooms (cremini or button work well), spinach, or a combination of both. Ensure any added vegetables are cooked down to remove excess moisture before layering them in the casserole.

→ What's the best way to reheat leftover Croque Monsieur Casserole?

Leftovers reheat beautifully in the oven. Cover the casserole dish loosely with foil and bake at 325°F (160°C) for 15-20 minutes, or until warmed through. For individual servings, a microwave can be used, but the oven will yield a crispier exterior.

→ My casserole turned out a bit soggy. What went wrong?

Sogginess can occur if the bread is not sufficiently buttered or if there's too much liquid. Ensure your béchamel is thick enough and that you press the bread down to help it absorb the egg mixture evenly. Also, avoid over-soaking the bread before baking. Proper baking time is crucial for a golden, set casserole.

→ What can I serve alongside this rich casserole?

This rich dish pairs wonderfully with a fresh, crisp green salad dressed with a light vinaigrette to cut through the richness. Steamed asparagus or a simple tomato salad also make excellent companions, offering a refreshing contrast.