Cut block of mozzarella in half. Using a box grater, shred one half of cheese; set aside. Cut the other half into twelve cubes; set aside. In a large mixing bowl, combine ground beef and next eight ingredients. Combine until all ingredients are thoroughly incorporated. Shape mixture into 12 (3-inch) balls. Press 1 cheese cube into center of ball, sealing it inside. Repeat for remaining 11 meatballs.
Heat butter and olive oil in heavy bottom skillet or cast-iron pan over medium heat. Gently place meatballs into pan, just to brown on each side, about 1 minute on each side. Once brown, remove and place on paper town lined baking sheet or plate to drain off excess fat.
Spray 12 regular size muffin cups with cooking spray. Unroll pizza dough per package directions. Using a 3-inch round cutter, cutout 12 rounds of pizza dough and press each firmly into bottom of each cup well. Dough will not cover sides completely. Place 1/2 tablespoon of marinara sauce in each muffin cup, top with 1 meatball, another 1/2 tablespoon of sauce and sprinkle of shredded mozzarella cheese. Repeat for remaining 11 meatballs. Bake on middle rack for 25-30 minutes, or until cheese is bubbly and browned. Remove from oven and garnish with fresh parsley. Serve immediately.