In a large bowl, whisk together the flour, cocoa powder, and baking powder. Whisk in the kosher salt and espresso powder. Set aside.

Line a baking sheet with plastic wrap and sprinkle with all-purpose flour or spray a large mixing bowl with nonstick spray. Set aside.

In the bowl of a stand mixer fitted with the paddle attachment, beat the granulated sugar and butter on high speed until fully incorporated.

Add the egg yolks and continue to beat on high until the mixture lightens and increases in volume, about 2 minutes. Scrape down the mixture to ensure even incorporation.

With the mixer on low, gradually add the dry ingredients to the bowl by large spoonfuls, alternating with spoonfuls of sour cream. Mix until just incorporated, avoiding excessive gluten development.

Transfer the dough to the prepared bowl or plastic wrap lined baking sheet. Sprinkle the top with all-purpose flour and cover. Refrigerate for 60 minutes.

Line a half-sheet baking pan with parchment paper and spray with nonstick spray. Dust a work surface with flour and turn out the dough onto it, floured side down.

Roll out the dough to ½ inch thick. Cut into donuts and holes using ring cutters. Place on the prepared sheet pan and cover with plastic wrap. Chill for at least 30 minutes.

In a medium bowl, whisk together the milk, powdered sugar, and salt. Cover with plastic wrap to prevent a skin from forming.

Heat oil in a fryer or Dutch oven to 350°F. Adjust heat to maintain the temperature between 350°-360°F.

Gently fry 3 donuts at a time, flipping after 30 seconds, and fry until evenly golden brown, about 80 seconds. Transfer to a wire rack.

Once cooled slightly, dip the donuts in the glaze and place back on the wire rack.