Croque Monsieur

1. Before you begin. You need to preheat the oven to 425°F (218°C) and line a baking sheet with parchment paper or a silicone baking mat.

Bechamel

1. Make a roux. First, melt the unsalted butter in a medium-sized saucepan over medium-low heat. Then whisk in the flour and continue to whisk for about 2 to 3 minutes until the mixture has thickened but is still very pale in color. It’s important not to cook the roux for too long or it will begin to darken in color.
2. Add the milk and seasonings. While continually whisking, pour in the warm scalded milk, nutmeg, and salt. Then continue to cook the mixture for another 5 minutes while whisking often to both avoid lumps and to keep the sauce from sticking to the bottom of the saucepan. You can also turn the heat down if necessary and just cook it a tad longer if needed. You will know that the bechamel is done when it coats the back of a spoon. 
3. Add salt to taste. After the bechamel is made, taste it for salt and season to your liking. You may find that you don’t need any additional salt. This is completely a personal preference. 

Sandwich

1. Toast the bread. Lightly toast your bread slices. This step is optional, but I find it gives the sandwich a nicer crunch.
2. Spread the bechamel and Dijon. Spread 4 of the toasted bread slices with a layer of bechamel sauce all the way to the edges to cover the entire slice. Then spread each of the other 4 slices of toasted bread with about a teaspoon of Dijon mustard. Now, place the 4 slices with bechamel on the prepared baking sheet. 
3. Add the cheese and ham. Top each slice of bread with the bechamel sauce on the baking sheet with a handful of shredded gruyere, 3 slices of black forest ham, and then another handful of the Gruyere. Then place the other 4 slices of bread spread with Dijon on top of the 4 slices now topped with ham and cheese mustard side down.
4. Add more bechamel, cheese, and herbs. Top each assembled sandwich on the baking sheet with 2 to 3 more tablespoons of bechamel sauce and another handful of shredded cheese. Then to finish, sprinkle each sandwich with some Herbes de Provence.
5. Bake the sandwiches. Place the baking sheet in the preheated oven and bake the sandwiches for 5 to 7 minutes. Then turn the oven on to broil, and broil them for another 2 to 3 minutes or until the cheese is lightly golden brown in color.