trout with sauce nantaise

serves 4

3 shallots, peeled and finely chopped
30ml white wine vinegar
50ml white wine
100ml double cream
100g unsalted butter, cut into cubes, plus a spoonful
Sea salt and pepper
A splash of vegetable oil
4 trout fillets, skin on (you could use salmon, if you prefer)
3 tbsp chopped fresh herbs (a mixture of parsley, chives and tarragon is good)
A big bunch or bag of watercress

1 Put the shallots and wine vinegar into a saucepan with 50ml water. Bring to the boil and reduce until the liquid disappears without scorching the shallots. Add the wine and reduce by half.

2 Add the cream and bring to the boil. Add 50g butter and whisk until incorporated. Repeat with another 50g butter. The sauce should be thick, but not claggy. If it is too thick, add a splash of water to thin it. Remove from the heat and season with salt and pepper.

3 Heat a splash of oil in a large frying pan. Season the skin of the trout with sea salt and place skin side down in the pan. Cook over a medium heat for about 3 minutes, until the skin is crispy.

4 Turn the fish over and add a spoonful of butter to the pan. Turn the heat down to stop the butter burning. Cook more gently for another 3 or 4 minutes or until the fish is cooked.

5 Warm through the sauce and stir in the chopped herbs. Pour the sauce over the fish and serve with watercress.