Peel the potatoes. Boil the potatoes in hot water. Once boiled, potatoes have to be mashed and mixed to all other ingredients. When the dough is homogeneous, make donuts and let them rise on a floury tray or wooden board, covered by a cloth, for 2 hours at least, in a tempered place. After leavening, fry the donuts with sunflower oil. In the meanwhile, prepare a cup with some sugar. When the donut is ready, dry it well and cover with sugar.