In a bowl, mix together softened butter, parmesan cheese, garlic powder, and Italian seasoning.
Spread the butter mixture evenly on one side of each slice of bread.
Preheat a skillet over medium-low heat. Place one slice of bread butter-side down in the skillet.
Add a slice of mozzarella, followed by 6 slices of pepperoni, another slice of mozzarella, another 6 slices of pepperoni, and one more slice of mozzarella.
Top with another slice of bread, butter-side up.
Grill for 3-5 minutes on each side, or until golden brown and the cheese is melted.
Serve with warm pizza sauce for dipping.