Preheat Oven: Preheat oven to 350 degrees F (175 degrees C). Pull out and set aside a baking sheet and aluminum foil.
Slice Bread: Place loaf of bread on a cutting board. Using a serrated knife, make diagonal cuts about 1 inch apart across top of bread, being careful not to cut all the way through to bottom. Turn bread and make diagonal cuts in opposite direction to create a diamond pattern.
Prepare Garlic Butter: To a small bowl, add melted butter, minced garlic, parsley, salt, and pepper. Stir well to mix.
Spread Garlic Butter: Set bread atop a large piece of aluminum foil atop a baking sheet. Then, using a spoon, spoon garlic butter mixture into all the cuts in bread, ensuring it gets into all crevices.
Add Cheese: Stuff shredded mozzarella and grated Parmesan into all the cuts, distributing evenly.
Wrap Bread: Wrap bread in aluminum foil. Tear off and use additional aluminum foil as needed to ensure the bread is completely covered.
Bake Bread: Place wrapped bread on a baking sheet, transfer baking sheet to oven, and bake for 15 minutes.
Unwrap and Crisp: Carefully unwrap foil from top of bread and bake for additional 5 minutes, or until cheese is melted and bread is crispy.
Serve: Remove from oven and let cool slightly before serving. Pull apart pieces to enjoy.