In a large mixing bowl, combine the ground beef, ground pork, breadcrumbs, parmesan cheese, parsley, and the egg. Season with a pinch of salt and pepper. Mix until just combined.

Scoop small amounts of the mixture and roll them into tiny balls, about the size of a marble.

Heat a tablespoon of olive oil in a large Dutch oven over medium heat. Add the meatballs in batches and brown them on all sides for about 5 to 7 minutes. Remove them from the pot and set aside.

In the same pot, add the diced onions, carrots, and celery. Sauté for about 5 minutes until the onions become translucent.

Pour the chicken broth into the pot and bring to a boil. Reduce the heat to a simmer and add the meatballs back into the pot. Let simmer gently for 10 minutes.

Add the acini di pepe or orzo directly into the soup and cook according to package directions, usually about 8 to 10 minutes.

Once the pasta is tender, stir in the fresh spinach or chopped escarole and let wilt for about 1 to 2 minutes.

Taste the broth and adjust seasoning if necessary. Ladle into bowls and serve immediately.