In a large bowl, whisk together the flour, cocoa powder, and baking powder. Add the kosher salt and espresso powder, and set aside.

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

In a stand mixer bowl, beat the granulated sugar and butter on high speed until fully incorporated.

Add egg yolks and continue to beat on high until the mixture lightens and volume increases (about 2 minutes). Scrape the mixture down as needed.

With the mixer on low, gradually add the dry ingredients alternately with spoonfuls of sour cream until incorporated, being careful to not overmix.

Transfer the dough to the prepared bowl or baking sheet. Sprinkle the top with all-purpose flour, cover, and refrigerate for 60 minutes.

Line a half-sheet baking pan with parchment paper and spray with nonstick spray.

On a floured surface, roll out the dough to ½ inch thick. Use ring cutters to cut the donuts and holes. Place them on the prepared pan.

Cover the pan with plastic wrap and chill for at least 30 minutes to overnight.

In a medium bowl, whisk together the whole milk, powdered sugar, and salt. Cover the glaze to prevent it from hardening.

Heat oil in a fryer or Dutch oven to 350°F, ensuring it's at least 2 inches deep.

Fry 3 donuts at a time, adjusting to maintain the oil temperature. Fry until golden brown (about 30 seconds per side).

Once cooled slightly, dip each donut in the glaze and place on a wire rack to set.

Store donuts at room temperature with a cracked container, ideally best consumed the day they are fried.