Béchamel Sauce
1½ Tablespoons unsalted butter
1½ Tablespoons all purpose flour
1 cup plus 2 Tablespoons milk, heated
3 Tablespoons shredded Parmesan cheese
3 Tablespoons shredded Gruyère
Salt to taste

Sandwich
6 slices French or Italian loaf bread
6 to 9 slices (9 ounces) thinly sliced ham
Dijon mustard
1 cup (4 ounces) shredded Gruyère
Bèchamal sauce

Béchamel Sauce:   Melt the butter in a small saucepan over medium heat.  Add the flour and whisk until smooth, about 2 minutes.  Slowly whisk in the milk and cook until the mixture thickens.  Remove from heat; add the Parmesan and 3 Tablespoons shredded Gruyère, and whisk until smooth.  Correct seasonings; set aside.

Sandwich:   Preheat oven to 350°F.  Place bread slices on baking sheet and bake for 5 minutes.  Turn slices and bake for another 3 to 5 minutes, until lightly toasted.  Remove from oven.

Spread one side of each toasted piece of bread with dijon mustard (for a more subtle taste, spread only one slice per sandwich with  mustard).  Evenly place 2 to 3 ham slices and Gruyère on half the toasted bread.  Top each with the remaining bread slices, mustard-side down.  Place sandwiches on Release lined baking sheet.

Spread bèchamel sauce to cover the top of each sandwich, including the crust.  Sprinkle evenly with remaining Gruyère cheese.  Bake for 5 minutes at 350° F, then place under broiler until the cheese mixture on top is bubbling and lightly browned, about 4 to 5 minutes.  Remove from oven and serve.  Yield:  3 large sandwiches; or 6 half sandwiches.