Boiled potatoes puree while still warm by adding the butter and salt. Add enough flour to get the dough flexible, but be careful not to become too dry. Then knead the dough by hand and roll out of the non-stick surface - thickness is about 1.5 cm. Then cut the rolled out dough into circles (with a glass or cookie cutter). Pierce cut circles with a fork. Bake the pan with a thick bottom, coated with butter. Cook until browned, turn and repeat the procedure. * You can add a piece of cheese between two slices and bake them together.