Preheat oven to 350°. Line a baking sheet with parchment paper.
In a medium pot, boil potatoes with skins until fork-tender. Strain excess water; peel skins. Mash the potatoes and let cool.
In a medium bowl, whisk together salt, flours, baking powder, baking soda and spices. Set aside.
In a large bowl, combine mashed potato, sugars, sour cream and egg.
Add dry ingredients to potato mixture, and beat until just incorporated. Dough will be sticky. Let dough rest for 10 minutes.
Dust counter with all-purpose flour; roll out dough to ½-inch thickness.
Using a 3-inch circular cookie cutter, punch holes from dough and line them up on parchment-lined baking sheet. Take a 1-inch circular cookie cutter and punch holes in the center of the dough.
Bake 12–13 minutes, until donuts start to turn golden brown.
Remove from pan, and cool on a rack. Prepare topping.