Croque Monsieur Recipe

Warm the milk

Place 1 cup whole milk in a small saucepan and warm over low heat until just steaming but not boiling, about 3–4 minutes. Keep warm while you make the roux.

Make roux

In a separate medium saucepan, melt 3 tablespoons unsalted butter over medium-low heat. When the butter is melted and bubbling but not browned, add 3 tablespoons all-purpose flour and whisk constantly for 1–2 minutes to cook the raw flour taste; do not let it brown.

Finish bechamel

Gradually add the warmed milk to the roux in a thin steady stream while whisking vigorously to avoid lumps. Increase heat to medium and continue whisking until the sauce thickens and coats the back of a spoon, about 3–5 minutes. Reduce heat to low and stir in 1 teaspoon dry mustard powder, 1 teaspoon grated nutmeg, 1 teaspoon fine salt, and 1/2 teaspoon freshly ground black pepper. Taste and adjust seasoning. Keep sauce warm (very low heat) while assembling sandwiches; if it thickens too much, whisk in up to 1–2 tablespoons warm milk to loosen.

Preheat and prepare

Preheat your oven to 425°F (220°C). Line a rimmed baking sheet with parchment paper or lightly grease it. If you prefer a broiler finish, set the oven rack 6–8 inches from the broiler element and keep the broiler ready.

Butter and mustard

Spread one side of each of the 8 slices of bread with a thin layer of the softened butter (this will be the exterior). On the opposite (interior) side of 4 slices, spread about 1/2 teaspoon Dijon mustard on each slice.

Assemble sandwiches

On the mustard-spread slices, arrange 2 slices of ham per sandwich (divide the 8 slices of ham into 4 sandwiches). Sprinkle about 1/2 cup of grated Gruyère over the ham, then top with an optional thin slice of Emmental or additional Gruyère if using. Close each sandwich with the buttered bread slices so buttered sides face outward.

Pan-toast

Heat a large skillet or griddle over medium heat. Place the sandwiches seam-side down in the skillet and cook 2–3 minutes per side, pressing gently with a spatula, until the bread is golden brown and the cheese inside begins to melt. Alternatively, you may skip this step and proceed directly to oven baking for a slightly softer exterior.

Top with bechamel and cheese

Place the lightly toasted or untoasted sandwiches on the prepared baking sheet. Spoon a generous 2 to 3 tablespoons of the warm béchamel sauce over the top of each sandwich, spreading it to cover the full top surface. Sprinkle the remaining grated Gruyère (about 2 to 3 tablespoons per sandwich, reserving roughly 1/2 cup total) evenly over the béchamel. Grind a little additional black pepper over each.

Bake and brown

Bake in the preheated 425°F (220°C) oven until the sauce is bubbling and the top is golden brown, 6–10 minutes. For a deeply browned crust, switch the oven to broil for 1–2 minutes, watching carefully to avoid burning, until the cheese topping is nicely browned and bubbling.

Rest and serve

Remove the Croque Monsieur from the oven and let rest on the baking sheet 1–2 minutes to set. If desired, sprinkle with 1 tablespoon finely chopped parsley. Cut each sandwich in half diagonally and serve immediately with a simple green salad dressed with vinaigrette.