To make the sauce soubise, sweat the onion in half the butter for 5 minutes. Add the vegetable stock and cook until tender. When soft, purée in a blender with the cream.
Season to taste and pass through a fine sieve. Reheat and whisk in the remaining butter piece by piece. Keep warm.
To make the mushroom essence, place the mushrooms, shallots, garlic and water in a saucepan and sweat down until a strong juice is obtained. Pass through a sieve, return to the pan, reduce by half and whisk in the butter piece by piece. Keep warm.
Place the turbot fillets in a saucepan, season and cover with the vegetable stock and dry white wine. Poach until just opaque. Drain well and arrange a portion on each plate. Pour a little sauce soubise around. Glaze the turbot with some mushrooms essence and garnish with the fresh herbs and spring onions.
© 1989 Kit Chapman. All rights reserved.