Step 1
Preheat oven to 400℉. In a large bowl, mix together celery, carrots, onions, garlic, parsley, bread crumbs, 1/4 cup Parmesan, egg, and ketchup and season with salt and pepper until well combined. Add beef and pork, mixing together by hand until just combined (don't over mix to maintain tender meatballs). Form 1 1/2" meatballs and place in an oven-safe dish or baking sheet. Do not overcrowd.