Preheat the oven to 350°F (175°C).
In a bowl, whisk together flour, cocoa powder, baking soda, and salt.
In a separate bowl, cream the softened butter with brown and granulated sugar until fluffy.
Add the egg and vanilla extract to the butter mixture; mix well.
Gradually add the dry ingredients to the wet ingredients, mixing until just combined.
Fold in the chocolate chips until evenly distributed.
Drop tablespoon-sized balls of dough onto a baking sheet lined with parchment paper.
Bake for 10-12 minutes, or until the edges are set but the center is soft.
Allow to cool on the baking sheet for a few minutes before transferring to a wire rack.