1 (1/4-oz) package active dry yeast (2 1/2 teaspoons)
2 tablespoons warm water (105–115°F)
pinch of sugar
3 1/4 to 3 3/4 cups all-purpose flour plus additional for sprinkling and rolling out dough
3 tablespoons sugar
1 1/2 teaspoons salt
1/2 teaspoon cinnamon
1 cup whole milk, at room temperature
1/4 cup + 1 tablespoon unsalted butter, melted until browned and cooled slightly
3 large egg yolks
About 10 cups vegetable oil for deep frying
2–4 cups granulated sugar for rolling and torching
Stir together yeast, warm water, and pinch of sugar in a small bowl until yeast is dissolved. Let stand until foamy, about 5 minutes. (If yeast doesn’t foam, discard and start over with new yeast.)
In the bowl of an electric stand mixer with a dough hook attachment, combie flour (3 1/4 cups), milk, butter, yolks, sugar, salt, cinnamon, and yeast mixture. I like to stir the mixture by hand, with a spatula, to loosely incorporate before transferring to the stand mixer to beat with the dough hook.
Beat at low speed on the mixer with the dough hook until a soft dough forms, about 3 minutes. Add a bit more flour if the dough seems too wet. It will tend to stick to the sides of the bowl a bit, but add flour it it seems overly wet and soft. Increase speed to medium and beat 5 minutes more.
Scrape dough down side of bowl (all around) into center, then sprinkle lightly with flour (to keep a crust from forming). Cover bowl with plastic wrap and a clean kitchen towel (not terry cloth) 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 and make fresh doughnuts in the morning.)
Turn dough out onto a lightly floured surface and roll out with a lightly floured rolling pin into a roughly 12-inch round (1/2 inch thick). Cut out as many rounds as possible with 1 1/2-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. They tend to get tough.
While the doughnut rounds rise, prepare your frying ingredients. Begin to heat your oil in a medium saucepan over medium heat. Spread sugar on a rimmed baking sheet for after the doughnuts have been fried.
Heat 2 1/2 inches oil in a deep 4-quart heavy pot until it registers 350°F on thermometer. A thermometer is key for this recipe. You need to know just how hot your oil is before the doughnuts fry. Fry doughnuts, 3 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 (1 minute per side). Transfer the freshly fried, hot doughnuts to the sugar and immediately toss to coat. Coating the doughnuts in sugar works best just out of the fryer so the sugar can stick to the hot oil. Remove from the sugar and allow to rest on a cooling rack before torching.
Return oil to 350°F between batches.
Once the doughnuts are all fried and generously coated in granulated sugar, using a kitchen torch to brûlée the tops of the doughnuts. Allow to cool and set before serving.