In a medium skillet set over medium-low heat, add the butter and melt. Place two pieces of toast side by side.
To each slice of bread, add a slice of mozzarella, 9 pepperoni, and another slice of mozzarella. Place remaining slices of bread on top.
Cook on each side for about 3 minutes or until the cheese is melty.
Meanwhile, make the garlic butter. In a small microwave safe bowl, add the butter. Heat until melted. Stir in parsley, Italian seasoning, garlic powder, and salt.
Using a pastry brush, brush on both sides of grilled cheese. Cook on each side for 30 seconds.
Remove, sprinkle with parmesan cheese and dip in your favorite marinara, if desired.