Clean and wash sugar snap peas, kohlrabi and carrots. Leave some green on the carrots. Finely dice the kohlrabi. Cover the carrots and cook in boiling salted water for about 10 minutes.
Add sugar snap peas and kohlrabi halfway through the cooking time. Wash the plaice, dab dry and sprinkle with lemon juice. Mix flour with some salt and pepper and turn the plaice in it. Heat some fat in a large pan and fry 2 plaice for about 6 minutes while turning them until crispy brown.
Keep the plaice warm and fry the two remaining plaice. Pluck the chervil leaves from the stems. Melt the remaining fat. Toss chervil, except for a few leaves for garnishing, and drained vegetables in it.
Season with salt and pepper. Arrange vegetables and mash on plates and serve garnished with lime and remaining chervil.