Idaho Potato Donuts

Place peeled, cubed Idaho russet potato in a small saucepan, cover with cold salted water, bring to a rolling boil over medium-high heat, and cook 12-15 minutes until a fork pierces cubes with no resistance. Drain completely, mash until entirely smooth (no lumps), measure out 170 grams (3/4 cup) of mashed potato, and set aside to cool to 21°C / 70°F (hot potato will kill yeast).

In a small bowl, combine warmed whole milk (43°C / 110°F), 1 teaspoon of granulated sugar, and active dry yeast. Stir gently, then let rest 5-7 minutes until a foamy, bubbly layer forms on top (proof that yeast is active). In the bowl of a stand mixer fitted with a dough hook, combine cooled mashed potato, the remaining 100 grams of dough sugar, melted cooled butter, lightly beaten eggs, 1 teaspoon ground cinnamon, nutmeg, and fine sea salt. Pour in the foamy yeast mixture, and stir on low speed to combine into a uniform wet base.

Gradually add all-purpose flour to the mixer bowl 60 grams (1/2 cup) at a time, mixing on low speed until a soft, slightly sticky dough forms that pulls cleanly away from the bowl sides (you may not need all 4 cups of flour; stop when dough is no longer gooey to the touch). Knead on medium-low speed for 5 minutes, then transfer dough to a lightly greased large glass bowl, cover with a clean damp cotton towel, and let rise in a draft-free 24°C / 75°F spot for 1 hour, until dough doubles in volume.

Once dough has doubled, punch it firmly in the center to release all trapped air, then turn out onto a lightly floured work surface. Roll dough to a uniform 1.25 cm (1/2 inch) thickness, then use a 7.5 cm (3 inch) donut cutter (or a round biscuit cutter paired with a 1 cm / 0.5 inch cutter for donut holes) to cut donut shapes. Re-roll dough scraps once to cut additional donuts, then place cut donuts and holes on a parchment-lined baking sheet, cover loosely with the damp towel, and let rest 20 minutes to puff slightly.

Heat neutral vegetable oil in a large heavy-bottomed Dutch oven or deep fryer to 175°C / 350°F, using a clip-on candy thermometer to monitor temperature consistently. Working in batches of 2-3 donuts at a time (do not crowd the pot, as this drops oil temperature and makes greasy donuts), fry 1.5 minutes per side until deep golden brown, flipping once with a slotted metal spoon. Remove fried donuts from oil, let drain 30 seconds on a wire rack set over a paper-towel-lined baking sheet. Adjust stove heat as needed to keep oil between 170-180°C / 340-355°F between batches.

While donuts are still warm (1 minute after draining, not piping hot), stir together the remaining 200 grams granulated sugar and 2 teaspoons ground cinnamon in a wide shallow ceramic bowl. Toss each donut and donut hole in the cinnamon sugar until fully coated on all sides, then return to the wire rack. Serve warm, within 2 hours of frying for the best light, fluffy texture.