Save to Pinterest My neighbor Sophie knocked on my door one Sunday morning holding a warm dish wrapped in a checked towel. She'd made too much, she said, and thought I might like to try her mother's version of croque monsieur turned into a casserole. One forkful of that golden, bubbling creation and I was completely sold. The creamy béchamel pooled around crisp-edged bread, the ham nestled between layers of nutty Gruyère, and I knew I had to learn how to make it myself. It's become my go-to whenever I need to feed a crowd without standing over the stove flipping sandwiches one by one.
I made this for a holiday brunch last December, and my cousin kept sneaking back to the kitchen for second and third helpings. He said it reminded him of the cafés we visited in Paris years ago, where we'd sit by fogged-up windows and order croque monsieurs with tiny cups of espresso. Now every time he visits, he asks if I'm making the casserole. It's funny how a dish can become part of your family's language like that.
Ingredients
- White sandwich bread: Removing the crusts helps the bread soak up the custard evenly, and using a sturdy white loaf prevents sogginess.
- Unsalted butter: Buttering each slice adds richness and helps the top layer turn golden and crisp in the oven.
- Gruyère cheese: This nutty, slightly sweet cheese is traditional and melts beautifully, though Swiss works well if Gruyère isn't available.
- Whole milk and heavy cream: Together they create a luscious custard that binds the layers and keeps everything moist.
- Large eggs: They give structure to the custard and help the casserole set as it bakes.
- Cooked ham: Use good quality deli ham or leftover holiday ham for the best flavor and texture.
- All-purpose flour: This thickens the béchamel sauce into a velvety coating for the top layer.
- Ground nutmeg: Just a whisper of nutmeg adds warmth and a classic French touch to the béchamel.
- Salt and black pepper: Season each component separately so every layer has balanced flavor.
Instructions
- Get the oven ready:
- Preheat your oven to 375°F and generously butter a 9x13-inch baking dish so nothing sticks. The butter also adds a subtle richness to the edges.
- Make the béchamel:
- Melt 2 tablespoons of butter in a saucepan over medium heat, whisk in the flour, and cook for about a minute until it smells toasty. Gradually pour in the milk while whisking constantly until the sauce thickens and coats the back of a spoon, then season with nutmeg, salt, and pepper.
- Butter the bread:
- Spread softened butter on one side of each slice after trimming off the crusts. This step might feel fussy, but it makes all the difference in texture.
- Build the first layer:
- Arrange half the bread slices buttered side down in the dish, then top with half the ham and half the grated Gruyère. Press gently so everything nestles together.
- Repeat the layers:
- Add the remaining bread buttered side down, then the rest of the ham and cheese. You're creating a sturdy, flavorful foundation.
- Pour the custard:
- Whisk together the eggs, milk, cream, and a pinch of salt, then pour this mixture evenly over the casserole. Press down gently with a spatula to help the bread absorb the liquid.
- Add the béchamel:
- Spoon the warm béchamel sauce over the top and spread it into an even layer. It will form a beautiful golden crust as it bakes.
- Bake until golden:
- Slide the dish into the oven and bake uncovered for 35 to 40 minutes until puffed, bubbling, and deeply golden on top. Let it rest for 10 minutes before serving so the layers set and slicing becomes easier.
Save to Pinterest The first time I served this at a potluck, a friend who claimed she didn't like ham asked for the recipe halfway through her first serving. She told me later that she made it for her book club and it disappeared in minutes. I love how this dish has a way of converting people, turning a simple brunch into something they remember and crave again.
Making It Your Own
You can easily swap the ham for turkey or leave it out entirely and tuck in sautéed mushrooms, wilted spinach, or caramelized onions for a vegetarian version. I've also spread a thin layer of Dijon mustard between the bread and ham for a sharper, more traditional croque monsieur flavor. Some people like adding a handful of fresh thyme leaves to the custard, which gives everything a subtle herbal note that works beautifully with the Gruyère.
Storing and Reheating
Leftovers keep well in the fridge for up to three days in an airtight container. I reheat individual portions in the oven at 350°F for about 15 minutes, covered with foil so they don't dry out. The microwave works in a pinch, but the oven brings back that crispy top layer. You can also assemble the entire casserole the night before, cover it tightly, and refrigerate it unbaked, then just add 10 minutes to the baking time when you're ready to cook it.
Serving Suggestions
This casserole feels special enough for a holiday brunch but simple enough for a lazy Sunday morning. I like to serve it with a crisp green salad dressed in a tangy vinaigrette to balance the richness, and a glass of chilled Chardonnay or sparkling water with lemon. Fresh fruit on the side, like sliced melon or berries, adds a bright, refreshing contrast.
- Pair it with a bitter green salad tossed in Dijon vinaigrette to cut through the creamy richness.
- Serve alongside roasted asparagus or green beans for a more elegant presentation.
- A basket of warm croissants and good butter makes the meal feel like a true French bistro experience.
Save to Pinterest Every time I pull this casserole out of the oven and see that golden, bubbling top, I think of Sophie and her checked towel. It's a dish that turns any morning into something worth lingering over.
Recipe Questions & Answers
- → Can I prepare this casserole ahead of time?
Yes, assemble the casserole up to 24 hours in advance. Cover tightly with plastic wrap and refrigerate. Add the béchamel sauce just before baking and increase baking time by 5-10 minutes if starting from cold.
- → What cheese works best if I can't find Gruyère?
Swiss cheese is the closest substitute with a similar nutty, mild flavor. Emmental, Comté, or a combination of fontina and Parmesan also work well for melting and flavor.
- → How do I prevent the bread from becoming soggy?
Use day-old bread that's slightly dried out, and butter each slice on one side to create a barrier. Don't over-soak the layers—just press gently to distribute the egg mixture without saturating completely.
- → Can I make this vegetarian?
Absolutely. Omit the ham and add sautéed mushrooms, caramelized onions, or blanched spinach between the layers. You can also use vegetarian deli slices for a similar texture.
- → What should I serve with this casserole?
A crisp green salad with Dijon vinaigrette balances the richness perfectly. Roasted asparagus, steamed green beans, or a simple arugula salad with lemon also complement the dish beautifully.
- → How do I store and reheat leftovers?
Store covered in the refrigerator for up to 3 days. Reheat individual portions in the microwave or the entire dish covered with foil in a 325°F oven for 20-25 minutes until warmed through.