Make the Garlic Parmesan Herbed Butter. Combine all ingredients under Garlic Parmesan Herbed Butter in a small bowl and stir until combined.
Lay the slices of bread on a baking sheet or sheet pan. Spread the Garlic Parmesan Herbed Butter on each side of every slice of bread.
Lay 2 slices of mozzarella on 4 slices of bread.
Lay 4 slices of pepperoni on each of the 4 slices of bread with cheese.
Add a small amount (about a teaspoon) of pizza sauce (or spaghetti sauce) on top of the cheese and pepperoni.
Cover the pepperoni and cheese with a slice of Garlic Parmesan buttered bread.Spread the Garlic Parmesan Herbed Butter on the top slice of bread.
Bake in a preheated oven until the bread turns golden brown and the cheese melts, which may take about 7-8 minutes.
Use a good quality cheese that melts well. I used Mozzarella because that is typically used on pizza and it melts well. However, you could also use American, cheddar, white cheddar, gouda, fontina, etc.
If you don't have sliced cheese, you can also use shredded cheese that would even help it melt even better.
I used Texas toast for the bread because I wanted to have that garlic bread feel and I didn't want the bread to be too thin. However, you can use regular white bread, wheat bread, or just about any other type of bread. As always, the better the quality of bread, the better the end result.
If you don't have pizza sauce, use spaghetti sauce.
You could use regular butter instead of the Garlic Parmesan Herbed Butter, but if you have all the ingredients, I recommend taking a couple of extra minutes and making the Garlic Parmesan Herbed Butter because it adds so much extra flavor.
Watch the grilled cheese sandwich while it is in the oven. Don't walk away. The baking time can vary depending on a number of factors, including the type of bread, thickness of the bread, the type of cheese, the temperature variation of your oven, etc. Watch it carefully so you can pull it out when it is a nice golden brown and the cheese is melted.