In a large bowl, combine ground beef, breadcrumbs, Parmesan cheese, minced garlic, egg, milk, parsley, salt, and pepper. Mix gently until just combined.
Shape the mixture into 1-inch meatballs and set aside.
Heat olive oil in a large skillet over medium heat. Add meatballs and cook until browned on all sides.
Pour tomato sauce over the meatballs, lower heat, and let it simmer for 20 minutes, stirring occasionally.
Serve the meatballs hot, garnished with extra Parmesan cheese and parsley, if desired.
Notes
These meatballs can also be served over spaghetti for a hearty meal.