Mini Meatball Sandwiches

INGREDIENTS

• Freshly ground black pepper
• 1/2 teaspoon salt
• 2 cups grated mozzarella
• 2 tablespoons olive oil
• 1 large jar marinara sauce
• 1/2 medium onion, diced
• 1/2 cup milk
• 1/2 cup panko or other breadcrumbs
• 2 cloves garlic, minced
• 2 pounds ground chuck or ground beef
• 12 dinner rolls or slider rolls