Cook 30 small crayfish with a fine Mirepoix and butter as indicated for Bisque d’Ecrevisses to the end of Stage 1.
Reserve 10 shelled tails for the garnish and finely pound the remainder of the crayfish with the Mirepoix. Add this purée and the cooking liquor to 1 litre (1¾ pt or 4½ U.S. cups) Fish Velouté, pass through a fine sieve and then through a fine strainer.
Adjust the consistency with 2½ dl (9 fl oz or 1⅛ U.S. cups) clear fish stock made with sole bones. Reheat without boiling and finish with the liaison of 6 egg yolks and 2 dl (7 fl oz or ⅞ U.S. cup) cream and 150 g (5 oz) butter.