In a large bowl, combine the first seven ingredients. Crumble beef and pork over mixture and mix well. Shape into 1-1/2-in. balls. In a large skillet, cook meatballs in butter in batches until a thermometer reads 160°. Remove and keep warm.
In a small bowl, combine the sauce ingredients until blended. Stir into skillet. Bring to a boil; cook and stir for 2 minutes or until thickened. Serve with meatballs.