Put the turnips in boiling salted water and cook for 2 minutes. Add the carrots, Cook for a further 6 minutes then add the leeks and cook for a further 2 minutes. Drain, reserve and keep warm.
Cut each fillet of fish into 6 pieces. Place all the fish except the mussels in a steamer and steam for about 1—2 minutes until opaque and just firm to the touch.
To make the sauce, simply put the vegetable stock and crème fraîche in a saucepan, bring to the boil then whisk in the butter piece by piece. Simmer until the sauce has reached a good consistency. Cook the mussels in the sauce and remove when open, about 2—3 minutes. Remove the mussels and discard the shells.
To serve, spoon the sauce around the plates and arrange the fish and shellfish decoratively. Add the vegetables. Dot the diced tomato on the dish then sprinkle a little chopped chervil on to the sauce. Serve immediately.
© 1989 Kit Chapman. All rights reserved.