These donuts puff up visibly when they are ready to be removed from the frying oil.
- 3 1⁄4 cups (14 oz.) bread flour, sifted
- 3⁄4 cup cocoa powder
- 1 tsp. baking powder
- 1 tsp. baking soda
- 3⁄4 tsp. kosher salt
- 1⁄2 tsp. ground cinnamon
- 1 cup sugar
- 4 tbsp. unsalted butter, melted
- 3 oz. bittersweet chocolate, grated
- 2 tsp. vanilla extract
- 3⁄4 cup buttermilk
- 2 eggs, plus 2 yolks
- Canola oil, for forming and frying
- 3 oz. unsweetened chocolate, grated
- 2 cups confectioners' sugar
- 1⁄4 cup heavy cream
Whisk flour, powders, soda, salt, and cinnamon in a bowl; set aside. Combine sugar, butter, bittersweet chocolate, vanilla, buttermilk, eggs, and yolks in the bowl of a stand mixer fitted with a paddle attachment; beat until smooth. With the motor running, slowly add dry ingredients and mix until a soft, sticky dough forms.
Heat 2" oil in a 6-qt. saucepan until a deep-fry thermometer reads 350°. Using lightly oiled hands, roll about ¼ cup batter into a loose, sticky ball; pat gently into a disk. With your thumb, make a 1½" hole in the center of dough; carefully slide into oil and fry, flipping once, until puffed and golden, about 3 minutes. Using a slotted spoon, transfer to a baking sheet with a wire rack; repeat with remaining dough and let donuts cool completely.
Mix unsweetened chocolate and confectioners' sugar in a bowl. Bring cream and 2 tbsp. water to a boil in a 1-qt. pan over high heat. Pour cream over chocolate; let sit for 2 minutes without stirring, then whisk until smooth. Dip tops of donuts in glaze and return to rack until glaze is set.