Preheat oven to 320F. Line a large cookie sheet with parchment paper or a silicone baking mat. Set aside.
In a large mixing bowl add coco powder and powdered sugar. Stir until combined.
Separate the egg whites from the yolks and add in the dry ingredients.
To incorporate the egg whites into the batter, whisk them until the mixture becomes smooth and free of any clumps of powdered sugar. Initially, you may feel that there is not enough liquid, but keep stirring . The batter should be extremely thick and sticky. If the consistency of your batter seems a bit thin, you can add an additional ½ to 1 tablespoon of cocoa powder.
Cover and chill in the freezer for 10 minutes.
Drop a tablespoon of dough onto the prepared pan, spacing them 2 inch apart.
Bake for 15-18 minutes.
Let cookies cool on the cookie sheet and set fully before removing them. Store in an airtight container.