For the potato salad, wash the potatoes well, add cold water and salt. Cook slowly without a lid (this allows any earthy smell to escape) until soft. Strain, rinse with cold water and peel while still hot. Cut into even slices (best with potato or egg slicer).
Mix all ingredients for the marinade and mix loosely with the still warm potato slices. Decorate the potato salad as desired with onion rings and chives or cress.