Brown the Sausage
In a large soup pot over medium-high heat, cook the Italian sausage, breaking it up as it browns. Add the diced onion and continue cooking until the sausage is no longer pink and the onion is tender.Build the Broth
Stir in the chicken broth, water, diced tomatoes, mushrooms, and garlic powder. Bring the mixture to a full boil.Add the Tortellini
Stir the refrigerated cheese tortellini into the boiling soup. Reduce the heat to a gentle simmer, cover, and cook according to the package directions, about 5 minutes, until tender. Stir occasionally to prevent sticking.Add the Greens & Seasoning
Reduce the heat to low. Stir in the fresh spinach, dried sweet basil, and black pepper. Let the soup cook for 2–3 more minutes (with lid on), just until the spinach wilts.Serve
Ladle into bowls and top with shaved or shredded Parmesan cheese, if desired. Serve warm with breadsticks or garlic bread.