In a large bowl, combine meat, parmesan, garlic, basil and/or parsley, bread crumbs, seasonings, and eggs. Mix well but try not to overwork the meat.
Using a large 12" oven safe skillet, heat the olive oil over medium high heat. Use hands to shape large palm sized meatballs and gently set in hot oil. Cook all meatballs until crispy golden brown for 2-3 minutes per side (you will have to gently rotate each meatball several times). When the surface of each meatball has a fair amount of cooked exterior, set aside on plate.
Add the onion to the hot oil and use a wooden spoon to scrape the bottom of the pan. The moisture from the oven should allow all that wonderful flavor stuck to the pan to release. Once the onion has slightly browned, return meatballs to pan. Cover with sauce. Allow sauce to come to a simmer and then reduce heat to the lowest point that still allows a gentle simmer. Let the meatballs cook in the sauce, uncovered, for 20 minutes.
While the meatballs are cooking on the stove, preheat the oven to 400 degrees F.
Place the mozzarella in a single layer on top of the meatballs. Place in preheated oven and allow to cook for about 5 minutes until the cheese is melted through.
Garnish with additional basil and/or parsley. Serve atop pasta or with a bun to make an awesome meatball sub.