Preheat oven to 350 °F.
Line 2 large baking sheets with parchment paper and spray with cooking spray.
Combine confectioners sugar, cocoa powder, espresso powder and salt in a medium bowl.
Beat egg whites in a large mixing bowl with an electric mixer until soft peaks form.
Add vanilla. Fold in the cocoa powder mixture with a rubber spatula until combined.
Lastly fold in chocolate chunks.
Drop the batter by tablespoonful onto the prepared baking sheets, leaving about 2 inches between each cookie.
Bake one sheet at a time, until the cookies are just beginning to crack on top, 12 to 14 minutes.
Let cool slightly on the pan before transferring to a wire rack to cool completely. Recipe inspired by EatingWell.
