Peel and wash the potatoes and put them on skewers. Fry in hot oil, turning occasionally, for about 15 minutes. Season with salt and pepper. In the meantime, clean and wash the radishes and cucumber and, except for something to garnish, cut them into fine sticks.
Peel and chop the onions. Wash and chop the herbs. Mix quark and yoghurt with prepared ingredients. Season with salt, pepper and lemon juice. Arrange skewers and quark on plates.
Garnish with salad, radishes and cucumber.