If you want this soup to be fat-free, simply thicken it with cornstarch (or potato starch) and water. (Use ¼ cup cornstarch dissolved in ½ cup cold water and then add it to the hot broth at the end once all other ingredients have been added.  Then heat it until it bubbles and thickens). This is still a delicious soup made this way, just not quite as rich and creamy as the roux method.