Clean, slice and salt fish and let stand over night or several hours. Cook, following recipe for Boiled Fish. Drain and bone, reserving 1 cup of the fish liquid. Mix the rest of the ingredients and cook until smooth and thick. It must taste strong of vinegar and sugar, and more of either may be added to taste. Serve cold. Gingerbread for Fillings, is used in place of the gingersnaps.