Prepare 150 g (5 oz) Julienne of mixed carrot, celery and parsley root, place in a pan with 30 g (1 oz) butter and stew it without colour. Moisten with 7½ dl (1⅓ pt or 3¼ U.S. cups) Fish Stock and 2 dl (7 fl oz or ⅞ U.S. cup) white wine. Finish cooking the vegetables gently and pass the liquid through a strainer reserving the Julienne. Cut the fish into pieces, moisten with the cooking liquor from the vegetables and poach. Remove the fish from the liquid, strain the cooking liquor and reduce it by three-quarters to approximately 2½ dl (9 fl oz or 1⅛ U.S. cups). Add sufficient White Wine Sauce to give the right consistency or, if necessary, thicken with a little Beurre Manié and finish by lightly buttering the sauce; add the Julienne of vegetables and use it to coat the pieces of fish.