For the meatballs, place the bread crumbs, garlic, parsley, Romano, Parmesan, milk, egg, 1 teaspoon salt, and ½ teaspoon pepper in a food processor and blend.
In a bowl combine with meat and mix thoroughly by hand.
Form into 1- to 1¼-inch meatballs and fry in batches in a large skillet with olive oil. (You should have about 40 meatballs. They don’t have to be perfectly round.) Brown lightly and remove to a plate.
When all meatballs have been browned, return to pan, add ½ cup broth and keep on very low heat while preparing the soup.
In the meantime, for the soup, heat the olive oil over medium-low heat in a large heavy-bottomed soup pot.
Add the onion, carrots, and celery and sauté until softened, 5 to 6 minutes, stirring occasionally.
Add the chicken stock and bring to a boil.
Add the pasta to the simmering broth and cook for 6 to 8 minutes, until the pasta is tender.
Add the the meatballs to the soup and simmer for 1 minute.
Taste for salt and pepper.
Stir in the fresh spinach and cook for 1 minute, until the spinach is just wilted.
Ladle into soup bowls and sprinkle each serving with extra grated Parmesan cheese.