Wash the potatoes and cook in salted water for about 20 minutes. Then rinse and peel. Let it rest a little. Clean and wash spring onions and cut them into rings. Wash apples, quarter them and cut out the core.
Cut the flesh into cubes. Bring vinegar to the boil. Season with salt, pepper and sugar. Add apple pieces and oil. Cut potatoes into slices. Pour marinade over them. Add spring onions.
Mix everything carefully, cover and leave to stand for about 30 minutes. For the sauce, wash and chop the dill. Mix with the sour cream. Season to taste with salt and pepper. Arrange salad sprinkled with crab meat on a plate.
Garnish as desired with lamb's lettuce and apple slices. Serve with extra sauce.