Place the cheese slices in between the slices of bread.
Melt the butter in a microwave safe bowl. Stir in the Parmesan cheese. Brush one side of the bread with the Parmesan butter.
Place the sandwich, buttered side down, into the pan.
Brush the melted butter mixture onto the top half of the bread. Cook until both sides of bread are golden brown and cheese is melted, about 4 minutes per side.
For maximum melt, cover the pan for a few minutes with a lid during cooking, checking on it often.