Make roux: Melt butter in a separate small saucepan over medium heat, then turn the heat down to low. Add flour and cook, stirring almost constantly, for 3 minutes. Don't let it brown.

Add hot milk: While stirring, add half the milk. Once incorporated into the roux, mix in the remaining milk

Thicken: Mix for 30 seconds to a minute or until it thickens into a spreadable and soft butter-like consistency (ie. not runny). If you have lumps, whisk until gone. Remove from heat (it is OK if it cools). Add dijon, nutmeg, salt and pepper.

Dijon + Bechamel: Spread the dijon evenly over the 4 slices of bread. Spread half the béchamel over the 2 slices of bread, as though you are buttering them to make normal sandwiches! (Reserve half the béchamel for topping)

Ham + Cheese: Top 4 pieces of bread with a slice of gruyere or Swiss cheese each (fold as needed to make them fit). Top with ham and add a crack of pepper, and close the sandwich.

Pan Fry: Melt butter in a skillet over medium to medium-high heat. Place sandwiches in the skillet, and cook for 2 minutes, pressing down lightly with an egg flip or spatula, until a deep golden brown. Turn and cook the other side until golden brown. Add more cheese grated on top and serve

Serve: Add more, bechamel, and cheese grated on top and serve