Brown the sausage in a heavy pot then add the onion and cook for a few minutes more.
Add the garlic, red pepper flakes and herbs, turn the heat right down and cook for a minute, stirring all the time.
Whisk ½ cup of beef broth with the tomato paste, then add the rest of the beef broth as well as the chicken broth.
Stir in the tomatoes and tomato paste mixture.
Turn the heat up and bring the soup to a boil.
Turn the head down, add the cheese tortellini and simmer for 10 minutes or until cooked.
Take the pan off the heat, stir in the spinach or arugula, and season to taste.
Serve sprinkled with parmesan cheese and garnish with fresh herb sprigs if liked.