In a large mixing bowl, combine the ground beef, ground pork, chopped onion, bread crumbs, fresh parsley, Worcestershire sauce, salt, pepper, beaten egg, and milk. Mix until the ingredients are thoroughly incorporated. Shape the mixture into 18 meatballs, each about 2 inches in diameter.
Heat the vegetable oil in a skillet over medium heat. Once hot, add the meatballs and cook, turning them to brown on all sides. Once browned, remove the meatballs from the skillet and set them aside to drain excess fat.
Add the sauerkraut to the skillet, stirring it to heat through. Return the meatballs to the skillet, placing them on top of the sauerkraut. Cover and let simmer for 15-20 minutes, or until the meatballs are fully cooked. If necessary, add water to the skillet to maintain moisture during cooking.
Once the meatballs are cooked, sprinkle them with additional fresh parsley before serving.