In a bowl, combine beef, pork, breadcrumbs, Parmesan, onion, garlic, egg, parsley, salt, and pepper. Mix gently (don’t overwork).
Roll into ½-inch meatballs (about 20–25). Optional: Bake at 375°F (190°C) for 10 minutes or brown in the soup pot.
Heat olive oil in a large pot over medium heat. Add onion, carrots, and celery. Sauté for 5 minutes until softened.
Pour in broth and bring to a boil. Add meatballs and pasta. Reduce heat and simmer for 10 minutes until pasta is tender.
Stir in spinach/escarole and cook 2–3 minutes until wilted. Season with salt and pepper.
Ladle into bowls and top with extra Parmesan.