Preheat your oven to 350°F (175°C)—line baking sheets with parchment paper or silicone mats.
In a large mixing bowl, cream together the softened butter, granulated sugar, and brown sugar until light and fluffy.
Beat in the eggs one at a time, then stir in the vanilla extract.
In a separate bowl, whisk together the flour, cocoa powder, baking soda, and salt.
Gradually add the dry ingredients to the wet ingredients, mixing until just combined.
Drop rounded tablespoons of dough onto the prepared baking sheets, spacing them about 2 inches apart.
Bake in the preheated oven for 8-10 minutes, or until the edges are set but the centers are still soft. Do not overbake.
Allow the cookies to cool on the baking sheets for a few minutes before transferring them to wire racks to cool completely.