Heat olive oil in a small skillet over medium heat. Sauté onions until soft, then add garlic and cook until fragrant. Remove from heat and let cool.
In a large bowl, combine ground beef, parmesan cheese, Italian bread crumbs, milk, egg, seasonings, and the sautéed onions and garlic. Mix just until combined.
Form the mixture into small to medium-sized meatballs.
Heat a skillet over medium-high heat. Sear meatballs on all sides until browned.
Reduce heat to low. Add marina sauce and a sprinkle of parmesan cheese. Cover and simmer for 25- 30 minutes, or until fully cooked.
Garnish with fresh parsley. Serve and enjoy!