Preheat your oven to 350°F (175°C).
In a bowl, whisk together cocoa powder, flour, baking powder, and salt.
In a separate bowl, cream the softened butter with granulated sugar and brown sugar until fluffy.
Add the egg and vanilla extract to the butter mixture, mixing well.
Gradually add the dry ingredients to the wet ingredients until just combined.
Fold in the chocolate chips or chunks gently.
Drop rounded tablespoons of dough onto a lined baking sheet.
Bake for 10-12 minutes, until the edges are firm but the center is soft.
Allow the cookies to cool on the baking sheet for 5 minutes.
Transfer to a wire rack to cool completely.