ingredients2. Tip the watercress and onion into a liquidiser and blend until smooth. While the liquidiser is running, add the cream and low-fat cheese until the mixture is well blended.
3. Line a grill pan with lightly oiled foil and lay the plaice fillets on the grill rack inside it. Brush the fillets lightly with oil and season to taste.
4. Cook the fillets under a hot grill for 5-8 minutes, until just cooked through and lightly golden.
5. Meanwhile, pour the sauce back into the pan, reheat gently for 2 minutes, and turn into a small serving bowl.
6. Transfer the cooked fish to the heated plates, garnish with watercress sprigs and serve with the watercress sauce.