Whisk together the flour, cocoa powder, baking powder and salt in a medium bowl.Beat butter in a stand mixer until light and creamy, about 3 minutes.
Add sugar and cream for another 3-4 minutes until light and fluffy.
Add in egg and beat to combine.
Add in flour mixture and beat just until combine and the mixture starts to come together. Do not overmix - it should still be crumbly but if you press it together with your hands it will stick together.Divide dough in half and roll into 1 1/2 inch diameter logs. The dough should hold together; if it does not you can mix it a little more in the mixer but try not to turn it into a completely solid ball of dough.Wrap logs in plastic wrap and chill for a couple hours until firm.Preheat ovens to 325 degrees F. Line baking sheets with parchment paper or silicone baking mats. Using a sharp knife, slice 1/2" thick rounds from the cookie logs.
Place cookies about 2 inches apart on baking sheets.
Bake for 10 to 12 minutes, rotating halfway through.