Wash the potatoes and cook in boiling salted water for about 20 minutes. Clean, peel, wash and halve carrots and cut them lengthwise into approx. 0.3 cm thick slices. Clean, wash and cut spring onions into 3 cm long pieces.
Cut the sugar snap peas diagonally in half. Chervil, except for a few leaves for garnishing, chop finely. Knead with butter and flour and chill. Blanch the carrots, mangetouts and spring onions in plenty of bubbling salted water for 2 minutes.
Pour into cold water and drain on a sieve. Wash the fish, dab dry and cut into pieces. Sprinkle with lemon juice, season with salt and turn in flour. Drain the potatoes, peel and cut in half.
Heat the oil in a pan. Fry the potatoes in it until golden brown and take them out. Then fry the fish pieces in the pan on both sides and take them out. Pour wine into the pan, season with vegetable stock, bring to the boil.
Add cream, bring to the boil again and thicken with the flour-butter. Warm the fish, potatoes and vegetables in the sauce and serve garnished with chervil leaves.