Place the fillets into a frying pan, pouring over enough water to cover and bring to the boil
Reduce the heat and simmer gently for 4-5 minutes, then remove from the water with a slotted spoon.
Heat the butter in a small saucepan, add the white wine and simmer until the liquid has reduced by half.
Add the fish stock and simmer until the liquid has reduced by half.
Add the double cream and cook gently for 1-2 minutes
Season with salt and pepper and stir well.
To serve, pour the white wine sauce over the fillets