Fish gelées are prepared with essentially the same methods used for meat gelées, except that veal feet are never cooked with the fish bones. (Fish bones cook in 30 minutes and veal feet take 6 hours.) Because the gelatin contained in fish bones rapidly dissolves into the surrounding liquid, it is rarely necessary to add extra gelatin.
Fish gelée has traditionally been prepared by making a double fish stock (moistening inexpensive fresh fish with a previously made stock) and then clarifying that stock with puréed whiting flesh (Escoffier called for fresh caviar!) and egg whites in the same way as for meat stock. Excellent fish gelée can still be prepared using this method, but the danger lies in the unavailability of fresh ingredients. Because the fish flavors will be intensified by three moistenings, it is essential that the fish be impeccably fresh—caught the same morning—or the resulting gelée will have a strong fishy taste. Avoid, also, cooking the fish bones too long—no more than 20 minutes—or the gelée will taste too fishy.