Save My mother-in-law once served this at a Sunday brunch, and I watched six adults go completely silent for ten minutes. No one had expected a casserole to taste like the elegant croque monsieur we'd shared in Paris years before, but here it was—golden, bubbling, impossibly rich. She winked at me across the table and said it was her secret weapon for feeding a crowd without standing over a skillet flipping sandwiches. I asked for the recipe before dessert even arrived.
The first time I made this for my book club, I panicked halfway through assembly because the bread looked too soggy. I almost started over, but I trusted the process and slid it into the oven anyway. It emerged puffed and golden, with crispy edges and a custardy center that made everyone ask if I'd trained in France. I hadn't, but I let them believe it for a moment.
Ingredients
- White sandwich bread: Removing the crusts isn't fussy, it's practical because they can turn leathery in the custard, and softer bread soaks up the egg mixture perfectly.
- Unsalted butter: You'll use it to grease the dish, butter the bread, and build the béchamel, so having it at room temperature makes everything easier.
- Gruyère cheese: This is the soul of a croque monsieur with its nutty, slightly sweet flavor, but Swiss works beautifully if Gruyère isn't available or feels too pricey.
- Whole milk and heavy cream: The custard base needs richness to stand up to the cheese and ham, and whole milk alone won't give you that luxurious texture.
- Large eggs: They bind the custard and puff slightly as it bakes, creating that airy, soufflé-like quality in the center.
- Cooked ham: Deli ham works perfectly here, just make sure it's good quality because you'll taste every slice.
- All-purpose flour: This thickens the béchamel, and cooking it for a full minute prevents any raw flour taste from sneaking through.
- Ground nutmeg: Just a whisper of nutmeg makes the béchamel taste like it came from a French kitchen, warm and subtly spiced.
- Salt and black pepper: Season every layer because bland béchamel or unseasoned custard will flatten the whole dish.
Instructions
- Get the oven ready:
- Preheat to 375°F and butter your baking dish generously so nothing sticks when you serve those first beautiful squares. A 9x13-inch dish is ideal because it gives you the right bread-to-custard ratio.
- Make the béchamel:
- Melt butter over medium heat, whisk in flour, and cook for one full minute while stirring to get rid of that raw taste. Slowly pour in the milk, whisking constantly, until it thickens into a smooth, velvety sauce that coats the back of a spoon, then season it with nutmeg, salt, and pepper before setting it aside.
- Butter the bread:
- Spread softened butter on one side of each slice, which creates little pockets of richness and helps the top layer crisp up beautifully in the oven. Lay half the slices buttered side down in the dish.
- Layer the fillings:
- Arrange half the ham over the bread, then sprinkle half the Gruyère on top. Repeat with the remaining bread, ham, and cheese, pressing gently so everything nestles together.
- Pour the custard:
- Whisk together eggs, milk, cream, and a pinch of salt until smooth, then pour it evenly over the casserole, pressing down gently so the bread absorbs the liquid. Let it sit for a minute if you have time.
- Add the béchamel:
- Spoon the sauce over the top and spread it gently with the back of a spoon so it covers everything. It will melt into the layers as it bakes, creating pockets of creamy richness.
- Bake until golden:
- Slide the dish into the oven and bake uncovered for 35 to 40 minutes, until the top is puffed, golden brown, and bubbling at the edges. Let it rest for 10 minutes before cutting so the custard sets and you get clean, beautiful squares.
Save One rainy Saturday, I made this casserole for a friend who'd just had a baby, and she texted me later that night saying her husband had eaten three servings and declared it better than their honeymoon in Lyon. I laughed, but I also understood because this dish has a way of turning an ordinary meal into something you remember, something that feels like care made visible.
Make It Your Own
I've swapped the ham for turkey when cooking for someone who doesn't eat pork, and I've also made a vegetarian version with sautéed mushrooms and spinach that my sister requests every time she visits. A thin layer of Dijon mustard spread between the bread layers adds a sharp, tangy kick that makes the richness even more balanced. If you want to go full decadence, sprinkle a handful of extra Gruyère on top halfway through baking for a cheesy, caramelized crust.
Timing and Storage
You can assemble this casserole the night before, cover it tightly with plastic wrap, and refrigerate it until you're ready to bake. Just add 10 minutes to the baking time if it's going into the oven cold. Leftovers keep in the fridge for up to three days, and I reheat individual portions in a 350°F oven for about 15 minutes so they stay crispy on top instead of turning soggy in the microwave.
Serving Suggestions
This casserole shines at brunch with a simple arugula salad dressed in lemon vinaigrette to cut through the richness, and it's hearty enough for dinner if you add roasted asparagus or green beans on the side. I love serving it with a chilled glass of Chardonnay or even a light beer if the occasion is casual.
- Pair it with a crisp green salad tossed in Dijon vinaigrette for balance.
- Serve it alongside roasted vegetables like asparagus, broccoli, or Brussels sprouts.
- Offer crusty bread and good butter for anyone who wants to soak up every bit of sauce on their plate.
Save This casserole has become my answer to every potluck invitation, every lazy Sunday morning, and every time I want to feel like I've made something special without spending hours in the kitchen. I hope it does the same for you.
Recipe FAQs
- → Can I prepare this casserole ahead of time?
Yes, assemble the casserole completely, cover with plastic wrap, and refrigerate for up to 12 hours. Bake directly from the fridge, adding 5-10 minutes to the cooking time until golden and bubbling.
- → What's the best bread to use?
White sandwich bread works best as it absorbs the egg custard evenly. Brioche or challah can add richness. Avoid thick-crusted artisan breads as they won't soak properly.
- → How do I make a vegetarian version?
Omit the ham and add sautéed mushrooms, spinach, or caramelized onions for depth. You can also substitute with vegetarian ham. The béchamel and cheese provide plenty of richness and umami.
- → Can I use regular cheddar instead of Gruyère?
While Gruyère has a distinctive nutty flavor, Swiss cheese is the closest substitute. Sharp cheddar works but delivers a sharper taste. A blend of cheeses adds complexity.
- → Why is my casserole watery after baking?
This happens when the egg custard isn't fully set. Ensure you bake for 35-40 minutes until puffed and the center is firm when gently shaken. Don't skip the 10-minute rest period, which allows carryover cooking and firming.
- → What wine pairs well with this dish?
Crisp whites like Chardonnay, Sauvignon Blanc, or Pinot Grigio complement the rich, creamy casserole perfectly. For reds, try a light Pinot Noir. The acidity cuts through the richness beautifully.