1 (1/4-oz) package active dry yeast (2 1/2 teaspoons)
2 tablespoons warm water (105–115°F)
3 1/4 cups all-purpose flour plus additional for sprinkling and rolling out dough
1 cup whole milk at room temperature
1/2 stick (1/4 cup) unsalted butter, softened
3 large egg yolks
2 tablespoons sugar
1 3/4 teaspoons salt, divided
1/2 teaspoon cinnamon
About 10 cups vegetable oil for deep-frying
1/4 cup boiling-hot water
5 teaspoons instant-espresso powder or instant-coffee granules
1 1/2 cups confectioners sugar
1 tablespoon light corn syrup
1/4 teaspoon pure vanilla extract
About 1/4 cup sanding sugar (optional)
- Stir together yeast and warm water in a small bowl until yeast is dissolved. Let stand until foamy, about 5 minutes.
- Mix together flour, milk, butter, yolks, sugar, 1 1/2 teaspoons salt, cinnamon, and yeast mixture in mixer at low speed until a soft dough forms. Increase speed to medium-high and beat 3 minutes more.
- Scrape dough down side of bowl into center, then sprinkle lightly with flour. Cover bowl with a clean kitchen towel and let dough rise in a draft-free place at warm room temperature until doubled in bulk, 1 1/2 to 2 hours. (Alternatively, let dough rise in bowl in refrigerator 8 to 12 hours.)
- Turn dough out onto a lightly floured surface and roll out with a lightly floured rolling pin into a 12-inch round (1/2 inch thick). Cut out as many rounds as possible with 3-inch cutter, then cut a hole in center of each round with 1-inch cutter and transfer doughnuts to a lightly floured large baking sheet. Cover doughnuts with a clean kitchen towel and let rise in a draft-free place at warm room temperature until slightly puffed, about 30 minutes (45 minutes if dough was cold when cutting out doughnuts). Do not reroll scraps.
- Heat 2 1/2 inches oil in a deep 4-quart heavy pot until it registers 350°F on thermometer. Fry doughnuts, 2 at a time, turning occasionally with a wire or mesh skimmer or a slotted spoon, until puffed and golden brown, about 2 minutes per batch. Transfer to paper towels to drain. (Return oil to 350°F between batches.)
- Stir together boiling-hot water and espresso powder in a medium bowl until powder is dissolved, then stir in confectioners sugar, corn syrup, vanilla, and salt until smooth.
- Dip doughnuts into glaze, turning to coat well, then put on a rack set in a shallow baking pan (to catch any drips). While glaze is wet, sprinkle doughnuts with sanding sugar (if using). Let stand until glaze is set, about 20 minutes.