Wash the potatoes thoroughly and cook in boiling water for 20-25 minutes. Drain, rinse and peel. Cut potatoes into slices. Peel onion and chop finely. Bring stock and onion to the boil, simmer for 2-3 minutes. Remove from the heat and pour over the potato slices. Leave to stand for approx. 45 minutes
In the meantime clean, wash and slice the radishes. Wash the sprouts and let them drain well in a sieve. For the vinaigrette, mix vinegar and mustard. Season with salt, pepper and sugar. Fold in 4 tablespoons of oil. Mix the potatoes, radishes and vinaigrette and leave to stand for a while
Wash the meat and dab dry. Heat 2-3 tablespoons of oil in a frying pan and fry the meat for 8-10 minutes at medium heat. Then season with salt and pepper.
Crumble bread. Wash herbs, shake dry. Finely chop parsley and chervil, except for some chervil for garnishing. Cut chives into fine rolls
Heat butter in a small pan and toast bread in it while turning. Mix in the herbs. Remove the meat from the pan, spread the herb crust evenly on top and press down lightly. Cut the meat open, arrange on plates with potato salad. Sprinkle salad with radish sprouts and garnish with chervil
Waiting time approx. 35 minutes