Heat the oven to 180 degrees Celsius. Boil the potatoes in their skins, peel them and mash. Mix with flour, egg, margarine or butter, salt and knead into a fluffy dough. Form dough into sausages about 2 centimetersthickness, cut into pieces. Place the dumplings in form and bake for about 45 minutes, lard (butter) in 20 minutes before done and pour sour cream over it.