Bring the pork loin covered with water to the boil and let it simmer at low heat for about 40 minutes. Wash potatoes thoroughly, cut into quarters lengthwise. Heat the oil in a pan and fry the potatoes for about 20 minutes, turning occasionally.
In the meantime, clean and wash the vegetables, peel the carrots so that some greenery remains. Cut the kohlrabi into slices. Cut zucchini lengthwise into thin slices with a peeler. Cook vegetables in salted water, blanch carrots and kohlrabi for 10 minutes, sugar snap peas for 5 minutes, zucchini for 2 minutes.
In the meantime, wash the herbs and pluck the leaves from the stems. Mix curd and yoghurt and add the herbs. Puree with the cutting stick of the hand mixer. Peel onion, dice finely and add to the sauce.
Flavour with horseradish, salt and pepper. Season potatoes with salt, pepper and caraway. Drain vegetables and meat. Cut the meat open and arrange on a plate with vegetables and potatoes.
Melt butter, pour over the meat and garnish with chervil.