Classic Croque Monsieur
- Make the Béchamel Sauce:
In a small saucepan, melt the butter over medium heat. Stir in the flour and whisk for about 1 minute to form a roux.
Gradually add warm milk while whisking continuously until the sauce thickens (about 3–5 minutes).
Season with nutmeg, salt, and pepper. Stir in the Parmesan cheese if using. Remove from heat and set aside. - Assemble the Sandwiches:
Lightly toast the bread slices in a pan or toaster to keep them from getting soggy.
Spread a thin layer of Dijon mustard on one side of 4 slices of bread (optional).
Layer each with ham slices and a generous amount of shredded Gruyère cheese.
Top with the remaining bread slices to form sandwiches. - Toast the Sandwiches:
In a skillet or griddle, melt butter over medium heat. Grill each sandwich for about 2–3 minutes per side until lightly golden (you don’t need to melt the cheese fully yet). - Top and Broil:
Preheat your oven broiler. Transfer the sandwiches to a baking sheet.
Spoon béchamel sauce over the top of each sandwich and sprinkle more shredded Gruyère on top.
Place under the broiler for 3–5 minutes until bubbly and golden brown. - Serve:
