Peel, wash and slice the potatoes. Fry the bacon cubes in a large pan without additional fat until crispy. Remove and put aside. Heat the oil in the frying fat. Cover and fry the potato slices for about 10 minutes, turning them over. Then open and fry for 5-8 minutes until crispy.
Rinse fish, pat dry and cut into pieces. Peel onions and cut into fine rings. Wash apples, quarter and core them. Cut apples and cucumbers into cubes. Stir sour cream, yoghurt and cucumber stock until smooth and mix with the prepared ingredients.
Season to taste with pepper, 1 pinch of sugar and possibly salt. Add bacon to the potatoes again. Season with salt and pepper. Serve with matie.