Croque Monsieur Casserole

This croque monsieur casserole has all the marvelous flavors of the original sandwich–salty ham, rich cheese, piquant mustard, milky béchamel sauce. Instead of bread, we use croissants. It’s great for breakfast, but it works even better as lunch or a simple supper. C’est magnifique!

A cooked croque monsieur casserole in a white rectangular baking dish on a wooden board.

Now, I’ve gotten questions from some folks about whether you can use something other than croissants. My question always is, “Why?!” The answer is, yes, of course. But I’d suggest an enriched bread, such as brioche or challah. You want that little bit of extra richness for this marvelous dish.

☞ READ THE BLAHG POST: WHEN COSTCO GIVES YOU CROISSANTS, MAKE CROQUE MONSIEUR CASSEROLE

A person holding a finished croque monsieur casserole.

Croque Monsieur Casserole

A finished croque monsieur casserole in a white baking dish with a spoon resting inside.
Croque monsieur—that perennial French classic—is the little black dress of the bistro set. Here we've given it a string of pearls, if you will, by making it a breakfast bake and using croissants. This is insanely rich, so a small piece goes a long way. (Or in our house, a not-so-long way.)
David Leite

Prep 15 mins
Cook 1 hr
Chill 8 hrs
Total 9 hrs 15 mins
Breakfast
French
10 servings
556 kcal
5 / 3 votes
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Equipment

  • 9-by-13-inch (23-by-33-cm) casserole dish

Ingredients 

For the croque monsieur casserole

  • Butter for the dish
  • 7 large croissants (about 1 pound | 500 g)
  • Your favorite Dijon mustard
  • 14 slices deli ham (about 8 ounces | 230 g)
  • 8 ounces Gruyere, Emmenthaler, Jarlsburg, or Swiss cheese grated (about 2 cups)
  • 8 large eggs
  • 2 cups whole milk
  • Salt and freshly ground white pepper

For the béchamel sauce

  • 3 1/4 cups whole milk
  • 5 tablespoons (2 1/2 oz) unsalted butter
  • 5 tablespoons all-purpose flour
  • Pinch ground nutmeg
  • Salt and freshly ground black pepper

Directions
 

Make the croque monsieur casserole

  • Butter a 9-by-13-inch (23-by-33-cm) casserole dish.
  • Slice the croissants lengthwise and spread with a bit of mustard.
    Halved croissants, spread with mustard, in preparation for making a croque monsieur casserole.
  • Tuck 2 slices of ham and about 1/4 cup cheese inside each croissant.
    Halved croissants topped with ham and shredded cheese for a croque monsieur casserole.
  • Cut each croissant into quarters, and fit the pieces in the dish. Turn them different ways, so some have frilly slices of ham showing.
    An assembled croque monsieur casserole prior to baking.
  • In a large bowl, whisk the eggs, then pour in the milk and whisk to combine. Season lightly with salt and pepper.
  • Evenly pour the egg mixture over the croissant pieces. Press down with your hands to make sure all the liquid is absorbed. Cover with plastic wrap and refrigerate overnight.
    Egg custard being poured over ham and cheese croissants for a croque monsieur casserole.

Make the béchamel sauce

  • In a medium saucepan over medium heat, warm the milk just until a skin begins to form on top, but the milk isn't boiling.
  • Meanwhile, in another medium saucepan over medium heat, melt the butter. Add the flour and stir constantly until the mixture bubbles and brews, about 2 minutes.
  • Slowly pour the hot milk into the pan with the flour-butter mixture, whisking the whole time. Bring the mixture to a boil, then reduce to low and simmer until the béchamel thickens, 2 to 3 minutes more. Season with nutmeg, salt, and pepper.
  • Pour the sauce into a container, press plastic wrap against the surface to prevent a skin from forming, and let cool to room temperature. Refrigerate overnight.

Assemble the casserole

  • The next morning, remove the casserole and béchamel sauce from the refrigerator 30 minutes before baking. Crank the oven to 350°F (175°C).
  • Uncover the casserole and place it on a foil-lined rimmed baking sheet. Using a whisk, stir the béchamel to loosen it. Spread the sauce over the top, and sprinkle with the remaining cheese.
  • Bake the casserole until puffed and golden brown, 50 to 55 minutes.
    A cooked croque monsieur casserole.
  • Serve immediately.
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Notes

Can I freeze this croque monsieur casserole?

Indeedy you can. Bake the casserole and allow it to cool completely, wrap it in plastic, and then wrap it tightly with foil. The night before you plan on reheating the casserole, place it in the refrigerator to defrost overnight. Reheat the dish in a 325°F to 350°F (163°C to 175°C) oven until the temperature in the center is 165°F (74°C).

Show Nutrition

Serving: 1portionCalories: 556kcal (28%)Carbohydrates: 31g (10%)Protein: 25g (50%)Fat: 37g (57%)Saturated Fat: 20g (125%)Trans Fat: 1gCholesterol: 252mg (84%)Sodium: 727mg (32%)Potassium: 368mg (11%)Fiber: 1g (4%)Sugar: 12g (13%)Vitamin A: 1221IU (24%)Vitamin C: 1mg (1%)Calcium: 416mg (42%)Iron: 2mg (11%)

Recipe Testers' Reviews

This croque monsieur casserole packs a wallop of cozy. So rich and creamy, it epitomizes “comfort food.” With ingredients like croissants, Gruyere, eggs, and ham--it’s a dreamy strata that is high on the rich and velvety quotient. So much so, that it’s a dish that's perfect for entertaining and/or a special occasion, especially since all the components can be prepared ahead of time. I'd never eaten or prepared the classic croque monsieur dish but I had served a mushroom tartine version that had similar components and preparation. At the time, I suggested to my family that they should envision ham and cheese prepared the same way and they all swooned.

I could envision this dish being served for brunch, dinner, or part of a buffet. It's also an ideal dish to share with neighbors and friends who recently had a baby or are going through a difficult time. What a gift of love this would be!

With over twenty-plus years with my husband, I know when he likes something I've cooked for him, when he's not too thrilled with it, and when he REALLY loves it. This croque monsieur casserole would merit the REALLY-REALLY-loves-it category. How did I know? I never had to ask him what he thought of the dish. His Pavlovian response was "Mmmm, this is good," as soon as the warm gooey mass hit his mouth. And the "Oh boy, this is really good" comment muttered under his breath a few times throughout the meal—as if I weren't in the room with him—definitely gave it away

I decided to make one change—I ended up turning this luscious dish into a croque madame, adding a creamy, dreamy over-easy egg (cooked in butter) on top of the wedge of deliciousness. Maybe that's why hubby's eyes rolled back in his head? Who knows? I do know I'll be serving it again this week, sharing it with our neighbor, and making it again in the future—for brunch, lunch, and/or dinner. It would be a great potluck dish too!

I served it with a salad of butter lettuce, avocado, pistachios, orange segments, fresh dill and parsley, olive oil, red wine vinegar, salt, pepper, and the juice of the orange.


Originally published April 3, 2021

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Comments

  1. 5 stars
    This caught my eye and stuck with me immediately when it was posted after Easter. I assembled it some time ago and I finally got around to baking it this morning. It was terrific! A great choice for a brunch menu. The only last minute part was making a fresh béchamel.

    I layered very thinly sliced shallot and snipped chives under the béchamel because, why not? For the meat and cheese I used rolled prosciutto and provolone appies also left over from Easter. Just placed them in the “sandwiches” as they were. All my leftovers simply and deliciously combined into brunch!

    I turned the broiler element on for the last several minutes.

    We had the casserole with slices of those long mini San Marazano cherry tomatoes from Trader Joe’s which I tossed with chives and lightly smoked salt. It all combined to an easy, delicious, memorable brunch.

    I think this will become part of our Easter tradition for the future.

    1. Thanks, Rainey! I didn’t think that casserole could get any better, but I love that you made your leftovers work with it and put your own spin on it.

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