2 skinless kippers fillets, about 225 g (7 1/2 oz) each
oil, for brushing
100 g (4 oz) watercress
salt and pepper
5 tablespoons soured cream
1 teaspoon wholegrain mustard
pinch of caster sugar
1 tablespoon finely chopped red onion
Cook the potatoes in a saucepan of lightly salted boiling water for 12–15 minutes until just tender. Drain and cool under cold running water, then drain again.
Meanwhile, lightly brush the kipper fillets with oil and place under a preheated hot grill for 7–10 minutes until cooked through. Remove from the grill and flake the flesh, discarding any skin and bones.
Mix together the soured cream, mustard and sugar, then season with salt and pepper.
Arrange the potatoes, watercress and fish on serving plates. Scatter over the onion and spoon over the dressing to serve.