Add 2 tablespoons of the butter to a very large pan over medium-low heat until melted.
Add 4 slices of bread to the pan and cook for 1 to 2 minutes or until toasted and lightly browned.
Flip the bread over to cook on the other side.
On two of the pieces of toasted bread add 1 tablespoon of mustard to each spreading it around to cover.
Add 4-6 slices of ham to the top of the toast with mustard and then evenly spread/layer on as follows: 2 to 3 tablespoons of bechamel, ¼ cup shredded cheese, a slice of toasted bread, 3-4 tablespoons of bechamel and ¼ cup of shredded cheese.
Place under the broiler on high heat for 3 to 4 minutes or until the cheese is melted and browned.
Slice the sandwich and garnish optionally with chopped fresh parsley.
Repeat the process to make the other sandwiches.
Notes
Make-Ahead: This sandwich is meant to be eaten as soon as it comes out of the broiler, but it can be reheated easily.How to Store: Keep covered in the refrigerator for up to 3 days. This will not freeze well.How to Reheat: Place the sandwich on a cookie sheet tray and bake in the oven at 350° for 5-7 minutes or until hot and the cheese is melted.With the leftover bechamel sauce, you can make potatoes au gratin, chicken nachos, biscuits and gravy, or lasagna Bolognese.Since artisan bread has large slices, you will likely have to cook them in batches.