Wash the potatoes and cook in boiling salted water for about 20 minutes. Clean the carrots, leaving a little green. Peel and wash the carrots. Peel, wash, quarter and slice kohlrabi.
Cook the carrots and kohlrabi in boiling salted water for about 10 minutes. Wash the meat, dab dry and fry in the heated oil on both sides for about 4 minutes until golden brown. Season with salt and pepper, remove from the pan and keep warm.
Deglaze the meat with the stock, stir in sour cream, bring to the boil and let it boil down a little. Season the sauce with salt, pepper and lemon juice. Wash the chervil, except for a few leaves for garnishing, chop finely and stir into the sauce.
Drain the potatoes, rinse with cold water and remove the skin. Drain the vegetables as well. Heat the fat. Swivel vegetables and potatoes in it. Arrange turkey steaks with the vegetables, potatoes and sauce on plates.
Garnish with the remaining chervil and serve sprinkled with coloured pepper.