Croque Monsieur Casserole (Printable)

Buttery bread layered with ham, Gruyère, and béchamel sauce baked to golden perfection for a French bistro classic.

# Ingredient list:

→ Bread & Dairy

01 - 12 slices white sandwich bread, crusts removed
02 - 2 tablespoons unsalted butter, softened, plus extra for greasing
03 - 1.5 cups Gruyère cheese, grated
04 - 1 cup whole milk
05 - 0.5 cup heavy cream
06 - 3 large eggs

→ Meats

07 - 8 slices cooked ham, approximately 7 ounces

→ Béchamel Sauce

08 - 2 tablespoons unsalted butter
09 - 2 tablespoons all-purpose flour
10 - 1.25 cups whole milk
11 - 0.25 teaspoon ground nutmeg
12 - Salt and black pepper to taste

# Cooking steps:

01 - Preheat oven to 375°F. Lightly butter a 9x13-inch baking dish and set aside.
02 - In a medium saucepan, melt 2 tablespoons butter over medium heat. Whisk in flour and cook for 1 minute. Gradually whisk in 1.25 cups milk, stirring constantly until thickened and smooth, approximately 3-4 minutes. Season with nutmeg, salt, and pepper. Remove from heat.
03 - Butter one side of each bread slice thoroughly.
04 - Arrange half the bread slices, buttered side down, in the prepared baking dish.
05 - Top bread with half the ham slices and half the Gruyère cheese.
06 - Layer remaining bread slices buttered side down, followed by remaining ham and cheese.
07 - Whisk together eggs, 1 cup milk, cream, and a pinch of salt in a bowl until well combined.
08 - Pour custard mixture evenly over the casserole, pressing gently to ensure bread absorbs the liquid.
09 - Pour béchamel sauce over the top layer and spread evenly across the surface.
10 - Bake uncovered for 35-40 minutes until puffed, golden brown, and bubbling at the edges.
11 - Allow casserole to rest for 10 minutes before serving to set the custard and allow easier portioning.

# Expert advice:

01 -
  • It gives you all the crispy, melty magic of a bistro sandwich without standing over a skillet flipping individual servings.
  • The custard-soaked bread becomes impossibly tender while the top turns golden and crackling.
  • You can assemble it the night before and just slide it into the oven when company arrives.
  • Leftovers reheat beautifully and taste even richer the next day.
02 -
  • If you skip the resting time after baking, the casserole will be too liquidy and fall apart when you scoop it.
  • Cold butter is impossible to spread on soft bread without tearing it, so let it sit on the counter while you gather everything else.
  • Whisking the milk into the roux slowly prevents lumps that no amount of stirring will fix later.
03 -
  • Grate the Gruyère yourself instead of buying pre-shredded, it melts more smoothly and tastes noticeably better.
  • Press the bread layers gently with a spatula after adding the custard to help it soak in evenly and avoid dry spots.
  • If the top browns too quickly, tent it loosely with foil for the last 10 minutes of baking.
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