Every region of France has its own fish soup or stew. The main differences, except for varieties of fish, are in the ingredients used to make the basic broth and the flavorful finishes sometimes added at the end. Again, the difference between a soup and a stew is simply a matter of the ratio of liquid to solid, less liquid being used to moisten a stew. To follow the continuum even further, a piece of fish with a concentrated sauce based on its head and bones is prepared in the same way as a fish soup or stew except that the liquid is highly reduced and perhaps finished, in the way of a sauce, with a little butter, cream, or beurre manié.