1. Cook the Italian sausage in a large saucepan over medium heat until browned. Cook the chopped onion and garlic until the onion is transparent.
2. Add the chicken broth, diced tomatoes, basil, salt, and pepper. Bring the soup to a boil, then lower to a simmer for around 10 minutes.
3. Add the tortellini and fresh spinach to the saucepan and boil for another 5-7 minutes, or until the tortellini is well cooked.
4. Serve hot and enjoy!