2Beat butter in a large mixing bowl using an electric mixer until creamy; add sugar, cocoa powder, and baking powder. Beat until combined. Scrape sides of bowl down if needed. Stir egg and vanilla extract into butter mixture until just combined; mix in flour.
3Fill the cookie press with dough; press cookies onto an ungreased baking sheet.
4Bake in the preheated oven until edges of cookies are lightly browned, 8 to 10 minutes.