- Servings: 14–16 doughnuts
- Prep Time: 20 minutes
- Cook Time: 2-4 minutes per doughnut
- 3 tablespoons unsalted butter, softened
- ¾ cup granulated sugar
- 1 large egg, at room temperature
- 1½ teaspoons vanilla extract
- 1 cup mashed cooked Yukon Gold potatoes
- ¼ cup buttermilk, at room temperature
- 1½ cups all-purpose flour, plus more for dusting
- ½ cup cake flour
- 1 teaspoon baking powder
- 1 teaspoon baking soda
- ½ teaspoon kosher salt
- ½ teaspoon grated nutmeg
- Vegetable oil, for frying
- Cinnamon sugar, for coating
1. In the bowl of a stand mixer ﬁtted with the paddle attachment, beat together the butter and granulated sugar on medium speed for 1 minute, until ﬂuffy.
2. Add the egg and vanilla and mix until pale yellow.
3. Add the mashed potatoes and buttermilk and beat until smooth.
4. Add the all-purpose ﬂour, cake ﬂour, baking powder, baking soda, salt, and nutmeg. Mix until combined. The dough will be sticky.
5. Dust a work surface with ﬂour. Place the dough on the counter and work a little bit of ﬂour into the dough to make it easier to work with.
6. Gently press the dough down with your hands to about ½ inch thick.
7. Using a doughnut cutter or two biscuit cutters (one large and one small), cut into rounds. Reroll scraps to use all the dough.
8. In a large pot or Dutch oven, heat 2½ inches of vegetable oil to 375°F. Line a baking sheet with paper towels.
9. Carefully place a few doughnuts at a time in the hot oil and cook for 2 to 4 minutes on each side, until puffy and golden.
10. Transfer the cooked doughnuts to the prepared baking sheet. Let them cool for a few minutes, then toss in cinnamon sugar. Serve.