Cut an oval piece out of top of each loaf. Reserve oval pieces for another use.
Combine meat and next 5 ingredients. Shape into 36 (1-inch) balls. Cook meatballs in a large nonstick skillet over medium heat 8 to 10 minutes or until browned on all sides. Remove from heat, and pat dry.
Preheat oven to 400°.
Return meatballs to pan; add pasta sauce. Cook over medium-low heat 10 minutes or until thoroughly heated.
Place loaves on a baking sheet; top each with 6 meatballs. Spoon sauce evenly over meatballs. Sprinkle evenly with cheese. Bake at 400° for 5 minutes or until cheese melts.