Cook 36 medium-sized crayfish as for Bisque; when cooked, remove and shell the tails and reserve 12 of the best carapaces for further use.
Finely pound all the remainder with the Mirepoix from the cooking of the crayfish. Add 15 g (½ oz) butter,
Pass this mixture through a fine sieve and place in a saucepan; place on ice and mix well, then fold in
Pour this mixture into a Charlotte mould which has been lined on the bottom and sides with greaseproof paper, reserving sufficient to fill the reserved carapaces. Fill the trimmed carapaces with this Mousse and decorate each with a round slice of truffle. Place the mould and crayfish in a refrigerator to set.
To serve, turn out the Mousse on to a low base made of rice or semolina set on a suitable dish. Carefully remove the paper from the Mousse and decorate the top with a border of round slices of truffle dipped in nearly setting Fish Aspic Jelly; surround the dish with a border of chopped jelly and place the prepared crayfish carapaces on it, standing almost upright.
place crushed ice in the outer container of the double timbale, replace the prepared inner container and present on a folded serviette on a round dish.