While sauce is simmering, cook the meatballs.
In a large bowl, combine the ground beef, beaten egg, parmesan cheese, parsley, salt, and pepper. Mix together until just combined.
In a medium bowl, combine the milk, breadcrumbs, garlic, and onion.
Add milk mixture to the meat mixture being careful not to overwork ingredients.
Form into 1-inch meatballs, greasing hands before starting to keep the meat from sticking, and place on a parchment-lined baking sheet.
Place in preheated oven and roast until the outsides are browned and they read 165°F on a meat thermometer (about 25 minutes).
Add baked meatballs to the spaghetti sauce. Toss to coat.
Serve over cooked noodles.