In a medium mixing bowl, whisk together the flour, sugar, cocoa powder, coffee, baking powder, and salt.

Add the butter. Use your fingers to work the butter into the dry ingredients. Once it resembles breadcrumbs, mix in the chopped chocolate.

In a separate smaller mixing bowl, whisk together the egg and vanilla.

Pour the egg mixture into the dry mixture. Use a rubber spatula to work the dough together. Once all the dry ingredients are moistened and a dough ball is formed, transfer the dough to plastic wrap. Wrap tightly and chill for at least 30 minutes in the refrigerator.

Preheat the oven to 375 degrees F. Line two large baking sheets with parchment paper.

Place the powdered sugar into a small mixing bowl.

Scoop a tablespoon of dough, roll it into a ball, and then roll the ball in the powdered sugar until it is generously coated.

Bake the cookies for 10 minutes. Allow 5 minutes for the cookies to cool on the baking sheet. Transfer to a wire rack to cool completely.