Croque Monsieur Casserole

My neighbor came back from Paris raving about a croque monsieur she had at a café near the Seine, and I wanted to recreate that magic without standing over a skillet flipping sandwiches for a crowd. That's when I started layering everything into a casserole dish, letting the oven do the work while I sipped coffee and set the table. The smell of bubbling Gruyère and buttery bread filled the kitchen, and suddenly it felt like we'd opened a little bistro in my dining room. Everyone scraped their plates clean, and I've been making it for brunch gatherings ever since. It's indulgent, fuss-free, and always impressive.

I made this for my sister's baby shower, and the quiet hum of conversation turned into outright requests for the recipe before I'd even brought out dessert. One friend stood at the counter with a fork, scraping up every last bit of béchamel from the dish. It reminded me that comfort food doesn't need to be complicated to feel special. That day, this casserole became my go-to whenever I want to feed people something warm and memorable without spending all morning in the kitchen.

Ingredients

• White sandwich bread: Use a soft, sturdy loaf and remove the crusts so the layers soak up the custard evenly without getting tough.
• Unsalted butter: Brushing each slice creates golden, crispy edges that contrast beautifully with the creamy center.
• Gruyère cheese: This nutty, melty cheese is traditional, but Swiss works just as well if that's what you have on hand.
• Cooked ham: Deli ham is perfect here, choose a good quality one with a little sweetness to balance the richness.
• Whole milk and heavy cream: Together they create a luscious custard that binds everything without feeling too heavy.
• Eggs: They give structure and turn this into something more than a pile of sandwiches, almost like a savory bread pudding.
• All-purpose flour: The base of your béchamel, whisked with butter to create a smooth, velvety sauce.
• Ground nutmeg: Just a pinch adds warmth and a subtle complexity that makes people wonder what the secret is.

Instructions

Prep the dish and oven:

Preheat your oven to 375°F and butter your baking dish generously so nothing sticks. This step also gives the bottom layer a little extra richness.

Make the béchamel:

Melt butter, whisk in flour, and let it bubble for a minute before slowly adding milk, stirring constantly until it thickens like warm silk. Season with nutmeg, salt, and pepper, then set it aside to cool slightly.

Butter and layer the bread:

Spread soft butter on one side of each slice, then arrange half the slices buttered side down in the dish. This creates a golden crust on the bottom while keeping the top soft enough to soak up custard.

Add ham and cheese:

Layer half the ham and half the Gruyère over the bread, then repeat with remaining bread, ham, and cheese. Press gently so everything nestles together.

Pour the custard:

Whisk eggs, milk, cream, and a pinch of salt, then pour it slowly over the casserole, pressing down lightly to help the bread absorb it. Let it sit for a few minutes if you have time.

Top with béchamel:

Spoon the sauce over the top and spread it evenly, it will melt into the layers and create a creamy, golden crust as it bakes.

Bake until golden:

Slide it into the oven uncovered and bake for 35 to 40 minutes until puffed, bubbling, and deeply golden on top. Let it rest for 10 minutes before serving so it sets up and slices cleanly.

Save

The first time I brought this to a potluck, someone asked if I'd trained in France. I laughed and told them it was just bread, cheese, and a little patience, but the truth is, this dish makes you look like you tried much harder than you did. It's become my secret weapon for impressing guests without breaking a sweat, and I love watching their faces when they take that first creamy, cheesy bite.

Make It Your Own

I've swapped the ham for turkey when cooking for friends who don't eat pork, and I've also gone fully vegetarian by adding sautéed mushrooms and spinach between the layers. A thin smear of Dijon mustard on the bread before layering adds a sharp, tangy kick that cuts through the richness. If you want to go all out, sprinkle a handful of Parmesan on top during the last 10 minutes of baking for an extra crispy, salty crust.

Prep Ahead Magic

This is one of those rare dishes that actually gets better when you assemble it the night before. I pour the custard over the layers, cover the dish tightly, and let it sit in the fridge overnight so the bread soaks up every drop. In the morning, I just make the béchamel, pour it on top, and bake while I brew coffee and set the table. It's transformed my brunch hosting from stressful to leisurely, and I can actually enjoy my guests instead of hovering over the stove.

Serving and Pairing

I like to serve this with a simple arugula salad dressed in lemon and olive oil, the peppery greens and bright acidity balance the richness beautifully. A chilled glass of Chardonnay or a crisp Sauvignon Blanc feels right, but honestly, a strong cup of coffee works just as well for a lazy weekend brunch.

• Let it cool for a full 10 minutes before slicing, or you'll end up with a delicious mess on the plate.
• Leftovers reheat beautifully in a low oven covered with foil, they stay creamy and don't dry out.
• If you're feeding a bigger crowd, double the recipe and use two dishes, it bakes at the same time and temperature.

Save

This casserole turns a simple stack of ingredients into something that feels like a warm hug on a plate. Make it once, and it'll earn a permanent spot in your brunch rotation.

Recipe Questions & Answers

→ Can I make this casserole ahead of time?

Yes, assemble the casserole up to 24 hours in advance, cover tightly, and refrigerate. Pour the béchamel sauce over just before baking and add 5-10 minutes to the cooking time.

→ What cheese works best if I can't find Gruyère?

Swiss cheese is the closest substitute with a similar nutty flavor. Emmental, Comté, or even sharp white cheddar also work well in this dish.

→ How do I know when the casserole is fully cooked?

The top should be golden brown and puffed, with the edges bubbling. The internal temperature should reach 160°F and the custard should be set, not runny.

→ Can I make a vegetarian version?

Absolutely. Omit the ham and add sautéed mushrooms, wilted spinach, or caramelized onions between the bread layers for a hearty vegetarian option.

→ What type of bread is best for this casserole?

White sandwich bread works perfectly as it soaks up the custard beautifully. Brioche or challah also make excellent choices for a richer, sweeter flavor.

→ How should I store leftovers?

Store covered in the refrigerator for up to 3 days. Reheat individual portions in the microwave or the entire casserole covered with foil at 350°F for 15-20 minutes.