- Preheat oven to 350 degrees Fahrenheit.
- In a large bowl, beat together mashed potato*, brown sugar, yogurt, and egg.
- In a separate bowl, whisk together flours, baking powder, nutmeg, baking soda and salt.
- Add dry ingredients to mashed potato mixture alternatively with buttermilk and beat until just incorporated (dough will be sticky.)
- Grease a 6 count donut pan with cooking spray. Fill each cavity with dough.
- Bake for 15 – 18 minutes until donuts start to turn golden brown. Remove from pan and cool on a rack.
- Repeat with remaining dough.
- Brush each donut with melted butter. Mix sugar and cinnamon together in a small bowl. Sprinkle each donut with about ¾ teaspoon of cinnamon sugar.
*For my mashed potato, I wrapped a russet potato in foil and baked in the oven for about 65 minutes at 400 degrees. I let it cool a bit and then mashed it for this recipe.