Wash the potatoes and cook in plenty of boiling water for about 20 minutes. In the meantime peel onion and cut into fine rings. Slice cucumbers into thin slices. Wash chives, dab dry and cut into fine rings.
Mix salad cream, yoghurt, approx. 5 tablespoons of cucumber water, 2/3 of the onion and chives, except for one tablespoon. Season to taste with salt and pepper. Add cucumber slices. Drain potatoes, rinse with cold water and peel.
Cut the potatoes into slices and add them to the sauce while still warm. Leave to soak for approx. 30 minutes. Clean, wash, drain and quarter the radishes. Wash and halve the apple and cut out the core.
Dice the apple halves. Add radish and apple to the salad. Roll up the herring fillets and pin them with a wooden skewer. Arrange on a plate together with the salad and sprinkle with the remaining onion rings.
Serve garnished as desired with apple slices and parsley.