Combine ground beef, Knorr® Homestyle Stock, Parmesan cheese, bread crumbs, egg and garlic in medium bowl; shape into 12 meatballs.
Bring Sauce to a boil over medium-high heat in large saucepan. Gently stir in uncooked meatballs.
Reduce heat to low and simmer, covered, until meatballs start to become firm, about 5 minutes. Turn meatballs gently, then simmer until done, stirring occasionally, about 15 minutes. Serve over hot spaghetti and sprinkle, if desired, with additional Parmesan cheese.