Add beef, pork, bread crumbs, parsley, oregano, half the Parmesan cheese, egg, salt, and pepper to a large mixing bowl. Use your hands to gently break up mixture and distribute ingredients. Shape mixture into small (1-inch) meatballs and transfer to a large baking tray drizzled with half the oil.
Place oven rack on highest shelf and turn oven to broil. Broil meatballs for 4 to 5 minutes, or until browned. Note that the meatballs will not be fully cooked, they'll continue to cook in the soup.
Add remaining oil to a large pot over medium high heat. Add celery, carrots and onion and saute for 8 minutes, or until softened. Stir in garlic and saute 2 minutes.
Pour in stock and bring mixture to a boil. Add pasta and meatballs to soup, reduce heat to medium low, cover, and cook until pasta is tender and meatballs are cooked through, about 10 minutes. Add spinach and stir until wilted. Divide soup into bowls and garnish with remaining Parmesan cheese. Enjoy!
This nutritional information refers to each serving of the entire recipe and not just the products used as ingredients.