In mixer beat eggs, sugar and potatoes until light and fluffy. Add oil and dry ingredients and mix well. Roll out on floured surface until desired thickness. Cut into doughnut shapes, reserving the holes. Fry in deep fat fryer at 350 degrees. Flip over when first side is golden brown and cook until the whole doughnut is golden brown. Drain on paper towel. Eat plain, with glaze or roll in cinnamon and sugar. Excellent eaten warm but will store in an airtight container up to one week.
Note: Sometimes your mashed potatoes may be dry or other times extremely wet. Adjust the flour added accordingly. I just made a batch this morning and it took 3 cups of flour to get the doughnuts to the roll out consistency.