Raised Potato Doughnuts

Yields 18 Doughnuts. Combine the dry yeast with warm water. Set aside. Heat the milk with the butter and sugar in a small saucepan until the butter begins to melt. Cool to lukewarm. Combine the mashed potatoes with the egg in a large bowl. Stir in the cooled milk mixture, the dissolved yeast and the salt. Gradually beat in enough of the flour to form a soft dough. Turn out onto a lightly floured board. Knead until smooth. Place in a lightly buttered bowl, turning to grease the entire outside surface. Cover. Let rise in a warm place until doubled in bulk (1-1 1/2 hours). Punch down. Knead again. Roll out on a lightly floured board to a thickness of 1/4 ". Cut out using a floured doughnut cutter. Cover. Let rise until doubled. Preheat the oil in the deep fryer. Fry doughnuts until browned on both side (about 2 minutes). Drain. Sprinkle with sugar.