In a bowl, mix the flour, baking powder, baking soda and salt. Set aside.
In a second bowl, whip the eggs and sugar with an electric mixer for about 1 minute, or until the mixture has become foamy. Add the butter and mashed potatoes, and mix. Add dry ingredients and blend until the dough is smooth. Using your hands, form two disks of dough. Cover with cellophane and chill for 1 hour.
Preheat the oil or fat in the fryer at 375 °F (190 °C). Line a baking sheet with cooking paper, and place a wire rack on a second baking sheet. Pour the maple syrup into a bowl and set aside.
On a floured surface and using a rolling pin, roll the dough to a thickness of about 1 centimeter. Cut the donuts using a round cookie cutter (about 3 inches), and then cut the donut holes with a smaller one (about ¾ inch). Let stand at room temperature for 15 minutes so the dough slightly dries and the donuts form a nice crust when fried.
Put the donuts 4 at a time in hot oil or fat, and fry for about 2 minutes or until golden in color, turning them halfway through cooking. Place on cooking paper and let cool for about 1 minute. Dip the donuts in maple syrup, place them on the rack and let stand. Repeat the same process for the donut holes, cooking them only for 1 minute.
Serve at room temperature and enjoy!
