Dissolve yeast in warm water, stir in sourdough starter, then let set.
In another bowl place scalded milk, sugar, margarine & salt; allow to cool.
Add starter mixture, mashed potatos & eggs; mix well.
Slowly stir in flour to make a soft dough, cover, and let rise until double.
Punch down, place on floured board; and knead.
Roll out to about 1/2 inch, cut and let rise again.
Fry in deep hot oil (365 degrees) until golden brown on each side.
Drain on paper; sugar while still warm.