Lay the onion on the bottom of a pan, add the parsley and put the turbot cutlets on top. Season well with salt and pepper and pour over enough water barely to cover. Lay some foil or a lid on top and poach very gently for 15 to 20 minutes, depending on the thickness of the cutlets. Leave in the water until needed.
Meanwhile, make the sauce by simmering in a double boiler the first 6 ingredients until the shallot is soft. In another saucepan melt the butter, stir in the flour and mix until smooth. Then add the first mixture and simmer, stirring all the time. When smooth and cooked, add the cream. Stir well, strain or liquidise and serve warm with the drained fish.
© 1988 Keith Floyd estate. All rights reserved.