From my story “Gold Star”
5 large eggs, separated
1 cup granulated sugar, divided
2 tablespoons instant espresso powder
1 tbsp unsweetened cocoa powder, plus more for dusting
½ cup cake flour
¼ tsp salt
Prepare two cookie sheets by lining with parchment paper.
Pre-heat the oven to 350˚F.
In the bowl of a stand mixer fitted with the whisk attachment, beat the egg yolks and ½ cup of the granulated sugar at medium speed until the yolks are pale and thick, about three minutes.
Add the espresso powder and cocoa powder and mix until completely absorbed, about 2 minutes.
Add the cake flour and mix on low briefly, just until the flour has been absorbed. (Err on the side of under mixing, and finish mixing by hand with a rubber scraper.) Mixture will be very thick. Transfer the mixture to a large mixing bowl.
Thoroughly clean the stand mixer bowl and whisk attachment. Add the egg whites to the bowl and beat the whites on medium high speed. When they have started to become frothy, slowly add the remaining ½ cup of granulated sugar and continue beating until the whites have reached stiff peak stage, about eight or nine minutes.
Fold the whites into the yolk mixture in two or three stages.
Cookies are shaped by either being piped through a pastry bag fitted with a wide, plain tip, or by carefully spooning the batter into small rounds onto the prepared cookie sheets.
Bake on the top shelf of the preheated oven for 14 to 15 minutes. Transfer on the parchment to racks and allow to cool thoroughly.