Wash the potatoes and cook in salted water for about 25 minutes. Drain, evaporate and peel. Cut cold potatoes into slices. Mix vinegar, stock, salt and pepper. Add oil drop by drop.
Mix vinaigrette and potatoes and leave to stand for about 3 hours. Boil eggs in boiling water for about 10 minutes. Quench, peel and cut into six. Wash herbs and dab dry. Pluck off leaves and chop coarsely. Cut chives into small rolls. Cut cress from the bed. Wash, clean and slice the radishes. Mix eggs, herbs and radishes with the potatoes. Season with salt and pepper and arrange on plates.
Cut chives into small rolls. Cut cress from the bed. Wash, clean and slice the radishes. Mix eggs, herbs and radishes with the potatoes. Season with salt and pepper and arrange on plates. Stir sour cream until smooth and put a blob on each herb-potato salad. Garnish with chives as desired