In a large stockpot or dutch oven (at least 6 quarts), brown the Italian sausage over medium heat.
Add the onion, garlic powder, and oregano. Cook, stirring frequently, until the onions are translucent.
Stir in the crushed tomatoes and chicken broth. Turn heat up to medium-high and bring to a boil.
Stir in the ditalini pasta and boil for 8 minutes or until just shy of al dente.
Stir the cornstarch into the milk to make a slurry. Pour into the soup, stir until it comes back to a boil.
Drop heat to low and stir in the spinach and parmesan cheese. Allow the spinach to wilt and the cheese to melt into the soup.
Serve with additional parmesan cheese if desired.
