Preheat your oven to 350°F (175°C).
In a medium bowl, whisk together the flour, cocoa powder, baking soda, and salt.
In a large bowl, cream together the softened butter, peanut butter, brown sugar, and granulated sugar until light and fluffy.
Add the egg and vanilla extract to the butter mixture. Mix until well combined.
Gradually add the dry mixture to the wet ingredients, mixing just until combined.
Fold in the chocolate chips gently into the dough.
Using a cookie scoop or spoon, drop tablespoon-sized mounds of dough onto a parchment-lined baking sheet, leaving space for spreading.
Bake for 10-12 minutes, until the edges are set but the centers look soft.
Remove from oven and let cool on the baking sheet for 5 minutes before transferring to a wire rack.
Enjoy warm, preferably with a scoop of vanilla ice cream on the side!