Peel and wash the potatoes and cook them in boiling salted water for about 20 minutes. Rinse the maties and cut into pieces. Wash, quarter, core and cut the apple into pieces. Cut cucumber into slices.
Put everything in a bowl. Mix yoghurt, sour cream and lemon juice. Season with salt, pepper and sugar. Wash the dill and chop finely, except for something to garnish. Stir the dill into the yoghurt sauce and pour over the salad ingredients.
Wash and chop the parsley. Drain the potatoes and sprinkle the parsley over them. Arrange matie salad and potatoes on a plate. Garnish with dill.