Wash the potatoes thoroughly and cook covered for about 20 minutes. Boil eggs hard. Then rinse and peel them.
Wash the dill and parsley, shake dry and chop finely. Wash and clean sorrel and shake dry. Put some small leaves aside for garnishing, chop the rest finely. Cut cress from the bed.
Finely chop the eggs. Set aside some egg and herbs for each. Mix the remaining herbs, yoghurt and sour cream. Season to taste with mustard, salt and pepper. Fold in eggs. Drain the potatoes, rinse and peel as desired.
Serve with roast beef cold cuts and sorrel sauce. Sprinkle with remaining chopped egg and herbs. Garnish with sorrel leaves.