For the meatballs

1. Soak bread. In a large bowl, stir the bread, milk, egg, and salt together until everything is evenly moistened. Let the mixture sit at room temperature until the bread is really soft, about 10 minutes.
2. Add meat and spices. Add the ground turkey, onion, cheese, garlic powder and dried parsley to the bread mixture. Mix gently with a rubber spatula until evenly combined.
3. Make meatballs. Shape the meat mixture into small meatballs about the size of a teaspoon (see Note 2).  If the meat mixture sticks to your hands too much, moisten hands slightly with water.
4. Chill. Place the meatballs on a silicone mat-lined or lightly greased cookie sheet, and refrigerate them while preparing the rest of the soup.

For the soup

1. Cook aromatics. Heat the olive oil in a very large (at least 6-quart) pot over medium heat. Add the onions and carrots. Sauté, stirring frequently, until the onions are translucent and beginning to brown, about 10 minutes. Add the garlic and cook until fragrant, about 1-2 minutes.
2. Simmer. Add the broth, oregano, and basil. Bring to a simmer and cook for 10 minutes.
3. Add spinach. Add the partially thawed chopped spinach, and bring the soup back to a simmer, breaking up any clumps of still frozen spinach.
4. Add meatballs. Gently drop the meatballs into the soup a few at a time. Simmer the soup for 30 minutes or so, then stir in the orzo pasta. Continue to simmer until pasta is al dente, about 8 minutes.
5. Season. Season the soup with salt and pepper to taste.
6. Serve. Serve the soup garnished with freshly grated Parmesan or Asiago cheese, if desired.