Preheat oven to 350°F. Line a rimmed baking sheet with aluminum foil or parchment paper and set aside.
To make the meatballs, place the ground beef in a large bowl, breaking up the meat into small pieces.
1 pound lean ground beef
Add the salt, pepper, onion powder, minced garlic, parsley, egg, Parmesan cheese, and bread crumbs.
1 teaspoon kosher salt, ½ teaspoon freshly ground black pepper, 2 teaspoons onion powder, 1 clove garlic, 1 Tablespoon dried parsley flakes, 1 large egg, ½ cup breadcrumbs, ½ cup parmesan cheese
Lightly mix until fully incorporated.
Shape into 12 meatballs about the size of a golf ball. Place on the prepared baking sheet about an inch apart. Bake for approximately 15-20 minutes.
While the meatballs are baking, make the sauce. Place the olive oil and pepperoni in a small saucepan over medium heat. Cook for about 3 minutes or so. Add garlic, and cook 1 minute more.
1 Tablespoon olive oil, ¼ cup finely chopped pepperoni, 1 clove garlic
Add tomatoes, basil, salt, pepper, and Parmesan cheese. Simmer for about 10 minutes to blend the flavors together. Set aside.
1 (14-ounce) can crushed tomatoes, ½ teaspoon dried basil, ¼ teaspoon kosher salt, Pinch of red pepper flakes, ¼ cup Parmesan cheese
Remove the buns from the package, and without separating them, use a long, serrated knife to cut the rolls in half horizontally. Place the bottom half of the rolls in a 9”x13” pan.
1 (12-pack) Hawaiian rolls
Layer 6 slices of mozzarella cheese on the bottom half of the bread.
12 thin slices provolone
Spread about ½ cup of the sauce in an even layer over the cheese on the buns. Place one meatball on each bun. Spoon another ½ cup of sauce on top, dividing it evenly over the meatballs. Reserve the remaining sauce for dipping.
Place the remaining 6 slices of cheese over the meatballs. Top with the remaining half of the buns.
Brush the buns with melted butter and sprinkle them with grated Parmesan cheese and parsley or chives.
2 Tablespoons salted butter, 1-2 Tablespoons parmesan cheese, 1 Tablespoon chopped fresh parsley
Bake for about 15 minutes, or until the cheese is melted and the buns are golden brown.