toast the bread
Toast the bread in your toasted until golden and crunchy.
Add butter to a saucepan and place over medium heat. When the butter melts, add the flour and stir with a whisk. Cook for 5 - 6 minutes while stirring regularly with a whisk. Pour in 80ml (1/3 cup) milk while whisking to get a smooth mixture. Pour the rest of the milk and season with salt, pepper, dijon, mustard, and nutmeg. Simmer for 6 - 8 minutes while stirring. Remove from the heat.
Spread a teaspoon of bechamel sauce over one slice of toast. Add a slice of cheese on top, followed by a slice of ham and another slice of cheese. Spread a teaspoon of bechamel sauce over the second slice of toast. Cover the ham with the toast with bechamel facing down. Now spread another teaspoon of bechamel sauce over the toasted bread and sprinkle with three tablespoons of grated cheese. Transfer the sandwich to a baking sheet lined with parchment paper and repeat the process with the rest of the ingredients.
bake and serve
Place a rack in the middle of the oven and preheat it to 190 °C / 375 °F. Add the sandwiches and bake for 10 - 12 minutes or until the cheese melts. Serve the sandwiches warm.