sentence: add butter and flour to a pot and stir sentence: add milk and whisk sentence: add parmesan cheese gruyere cheese black pepper salt and nutmeg sentence: spread butter on the bread slices and bake in the oven sentence: spread dijon mustard on half the slices sentence: add three slices of ham and gruyere cheese sentence: top with a slice of bread sentence: spread the bechamel sauce on top and add gruyere cheese sentence: bake in the oven