In a small microwave safe bowl combine the minced garlic, crushed red pepper flakes and 4 tablespoons unsalted butter.

Cover the bowl and microwave the garlic butter mixture for 1 minute, stirring halfway through. Cook another 15 to 30 seconds or until the butter is bubbling around the edges. Cool slightly.

Add the remaining room temperature butter, garlic powder and salt to the melted butter garlic mixture. Stir to create a paste. If needed, allow the butter to sit at room temperature until it solidifies and reaches spreading consistency.

While the butter is resting cut the bread in half lengthwise using a serrated knife. Place the bread cut-side-up on a large rimmed baking sheet. Spread the garlic butter mixture evenly between the two pieces of bread. Sprinkle the Parmesan evenly on each half.

Bake in the preheated oven until well browned around the edges, about 5 minutes.

Remove from the oven and slice each loaf crosswise into two-inch thick pieces. Reassemble the loaf so the sides of each slice are touching. Sprinkle the mozzarella cheese evenly over the toasted bread.

Move the oven rack up to the middle top position and turn the oven to broil. Return the pan to the oven and broil the bread until the mozzarella cheese is melted, bubbly and browned.

Remove from the oven and allow the bread to rest a few minutes before serving. Sprinkle with chopped parsley leaves, if using. Serve with pizza sauce or marinara for dipping, if desired.