Preheat your oven to 375°F (190°C).In a large mixing bowl, combine ground beef, ground pork, breadcrumbs, Parmesan cheese, parsley, egg, minced garlic, salt, and pepper.Mix until all ingredients are well combined.
Shape the mixture into small meatballs, about 1 inch in diameter.Place the meatballs on a baking sheet and bake for 15-20 minutes, or until they are cooked through and lightly browned.
While the meatballs are baking, heat olive oil in a large pot or Dutch oven over medium heat.
Add the chopped onion, carrots, and celery to the pot. Cook, stirring occasionally, until the vegetables are softened, about 5-7 minutes.
Pour the chicken broth into the pot with the cooked vegetables.Bring the broth to a boil, then reduce the heat and let it simmer for about 10 minutes.
Add the pasta to the simmering broth and cook according to the package instructions until al dente.Stir in the chopped spinach and let it cook until wilted, about 2-3 minutes.
Once the meatballs are cooked, add them to the soup.Let the soup simmer for another 5-10 minutes to allow the flavors to meld together.
In a small bowl, whisk together the eggs and Parmesan cheese.Slowly pour the egg mixture into the soup, stirring constantly, to create thin ribbons of egg.Season the soup with salt and pepper to taste.
Ladle the soup into bowls.Sprinkle with additional Parmesan cheese if desired.Serve hot and enjoy the comforting flavors of this Italian classic.