Preheat the oven to 350˚F. Set oven rack to center position. Line a baking sheet with parchment paper.
In a large bowl beat butter for 1 minute. Add sugar and brown sugar and beat an additional 2 minutes until fluffy.
Add the egg and vanilla and beat gently until combined.
In a small bowl combine flour, cocoa powder, baking powder and salt. Blend with a whisk or fork to make sure no lumps remain.
Add flour mixture to the butter and sugar mixture and gently blend until just combined and no streaks remain. Do not over mix.
Fold in chocolate chips/chunks and blend gently.
Place dough in small heaps, about 1 Tablespoon in size (easiest with a cookie scooper), on the baking sheet, leaving about 2" in between.
Bake for 10-12 minutes. The cookies should be golden brown and set.
Remove from oven and let rest on the baking sheet for 1 minute, remove to a cooling rack. Let cool completely and serve.
Store cookies in an airtight container, to keep fresh, for up to 3 days