The gel in gefilte fish is the broth in which the fish balls are cooked. The broth of gefilte fish is traditionally made up of fish head and bones, carrots, onions, water, salt, sugar and spices such as bay leaves, allspice berries and black pepper. After the gefilte fish is cooked it is strained and the remaining liquid is reduced to make a thick gelatinous substance. The gelatinous substance can then be used as a sauce for the gefilte fish, or it can be stored in jars to be used later. If you're not a fan of gelatin textures, feel free to skip this sauce!