Butter one side of each slice of bread with softened butter. On unbuttered side of one slice, spread on pizza sauce. Then add about 3 tablespoons of the mozzarella, lay out the pepperoni, and then top with the rest of the mozzarella and the other slice of bread. The buttered side should be on the outside. On one buttered side, spread 1 tablespoon of grated parmesan cheese and press down gently. Place this face down on a skillet or griddle heated over medium heat. Top the other buttered side (should be face up in the pan) with the rest of the parmesan cheese.
Cook for 4-6 minutes on each side or until golden brown and cheese on the inside is melted. Enjoy immediately.