MAKING
1)In a saucepan, boil potatoes in salted water until tender. Drain.
2)Keep aside 1 cup of water.
3)Take a large mixing bowl and pour water in it.
4)In a bowl, stir in sugar, salt and 1 cup of the flour and beat until smooth.
5)Add yeast to lukewarm water (warm, not hot, for active dry yeast; lukewarm for compressed yeast) and dissolve.
6)Add it into batter. Cover bowl with a cloth and let stand in a warm place until bubbly, about 4 hours.
7)Mash potatoes and measure 1 cup into a mixing bowl and add butter, eggs and nutmeg.
8)Mix potato mixture into yeast batter and add remaining flour or enough to make stiff dough.
9)On a lightly floured board and knead until smooth and elastic.
10)In a greased bowl, put the dough, cover and let rise in a warm place until double in bulk.
11)Punch dough down and store in refrigerator until ready to use.
12)Divide dough in half and roll each half out on a lightly floured board to about1/3 inch thick.
13)Cut with a doughnut cutter.
14)Place doughnuts on a floured board, cover with a cloth and let rise in a warm place until double in bulk.
15)Take a pan and heat fat in it, drop doughnuts one at a time and fry until golden. Drain.

SERVING
16)Sprinkle sugar, if desired and serve.