Salted doughnuts with different fillings

Potatoes are cooked the day before in the peel, cleaned and grated, mixed with yeast, flour, salt, eggs diluted in sweetened milk or sour cream. The dough is thoroughly kneaded until it moves away from the hands. It is left in a warm place for an hour to lift. The layer is rolled out with a thickness of a finger, mugs are cut into a glass, on which slides of ground bryns (cottage cheese or pieces of sausages) are placed, closed on top with another mug, the edges are pinched. The doughnuts are roasted in a pan of preheated fat. They must brown on both sides. Each doughnut is then sprinkled with grated parmesan.