Preparation

• 1
  1. First make the sauce. Peel and chop the onion very finely. Chop the celery very finely too. Melt 40g of butter in a saucepan and sauté the onion over a low heat for 5 minutes, then add the celery and cook for another 5 minutes until soft.
• 2
  2. Add the hot vegetables stock and simmer briskly for 8-10 minutes. Meanwhile, discard any tough stems from the watercress and chop it roughly.
• 3
  3. Add the watercress and 2 tablespoons of lemon juice then cook gently for just a minute or two. Pour into a blender and pulse several times. Return to the saucepan on a low heat and stir in the crème fraiche to thicken the sauce, then season well with salt and pepper. Turn off the heat whilst the fish is cooked.
• 4
  4. Heat the olive oil in a large frying pan and, when it is hot, place the trout fillets in the pan skin side down. Fry them for 3 minutes, or until the skin is crisp and golden brown. Carefully turn the trout over and fry for another 2 minutes, or until the fish is completely cooked through. Lift the fillets out carefully with a fish slice onto warmed plates.
• 5
  5. Reheat the watercress sauce, stirring in the remaining knob of butter, checking the thickness and the seasoning. Serve with the trout fillets. Garnish with a sprig of watercress and a wedge of lemon.