Peel and wash the potatoes and cook them in salted water for about 20 minutes. Hard boil the eggs in boiling water for 8-10 minutes.
Wash the herbs, pat dry, remove the stems if necessary and set aside 4 stalks of Pimpinelle for garnish. Finely chop all other herbs. Peel the onions and cut into fine cubes.
Drain, rinse and peel the eggs. Take the yolk out of 2 eggs and strain through a sieve, finely chop the egg white.
Put the herbs - except for 1 tablespoon for garnish - with onions, egg yolks and egg whites in a bowl. Add the vinegar, oil, sour cream and yoghurt. Mix everything well and season the sauce with salt, pepper and sugar.
Drain the potatoes and let them steam briefly. Halve the remaining eggs and arrange on serving plates with sauce and potatoes. Garnish with 1 stick of pimpinelle and the remaining herbs.