By Kit Chapman
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