To make Bechamel sauce, melt butter in a small saucepan. Add the flour, stir until the mixture bubbles. Whisk milk, salt and pepper into the flour mixture and simmer, whisking constantly, until the sauce is thickened.
Remove from heat and stir in 2 tbsp Gruyere cheese, 1 tbsp Parmesan cheese and nutmeg. Stir until cheeses melt.
To assemble sandwiches, spread ½ of the Bechamel sauce on two slices of bread. Top each slice with 2 slices of ham and sprinkle half of the remaining Gruyere over ham. Spread Dijon mustard on the remaining two slices of bread and place, mustard side down, on top of ham and cheese.
Put sandwiches on a baking sheet coated with non-stick cooking spray or lined with parchment paper. Cover with remaining Bechamel sauce and Gruyere cheese.
Bake for 5-7 minutes until cheese melts and the sandwich is heated through. Place under broiler for a few moments, if desired, to brown top of the sandwich.
For a Croque Madame: Top with a fried or poached egg.
Hack: Bechamel sauce can be stored in the refrigerator for up to 5 days. Cover surface with plastic wrap to avoid forming a skin.
Keyword Croque Madame, Croque Monsieur, French cuisine, French food, lunch, sandwich, toasted
Did you know? Croque Monsieur is the French equivalent of our grilled cheese. And just like grilled cheese, the Croque Madame is one of many variations!