To ensure these potato-based donuts turn out pillowy and soft after frying, take care not to overwork the dough.
- 1 large russet potato (about 10 oz.), peeled and cut into 1″ pieces
- 2 cups (9 oz.) all-purpose flour, sifted, plus more for dusting
- 1 1⁄2 tsp. baking powder
- 1 1⁄2 tsp. kosher salt
- 1 tsp. freshly ground black pepper
- 1⁄2 tsp. ground mace
- 1 cup sugar
- 2 eggs, lightly beaten
- 1⁄4 cup milk
- 2 tbsp. unsalted butter, melted
- 1 tsp. grated lemon zest
- Canola oil, for frying
Boil potato pieces in a 2-qt. pan of salted water until tender, 18 to 20 minutes. Drain; pass through a ricer into a bowl. Whisk flour, powder, ¾ tsp. salt, ¼ tsp. pepper, and mace in a bowl; set aside. Combine potato, ⅓ cup sugar, eggs, milk, butter, and zest in the bowl of a stand mixer fitted with a paddle attachment; beat until smooth. With motor running, slowly add dry ingredients and mix. Let dough rest 10 minutes.
Combine remaining salt, pepper, and sugar in a bowl; set aside. Heat 2″ oil in a 6-qt. pan until a deep-fry thermometer reads 370° On a lightly floured surface, using your hands, pat dough into a 10″ round about ½″ thick. Using a floured 3″ donut cutter, cut out donuts; gather and reuse scraps. Working in batches, place donuts in oil. Cook, flipping once, until puffed and golden, 3 to 4 minutes. Using a slotted spoon, transfer to a baking sheet with a wire rack; let cool completely. Toss in sugar mixture.