Preheat the oven to 375 degrees F. Line 3 baking sheets with parchment paper.
In a stand mixer, combine the butter, brown sugar, granulated sugar, vanilla and eggs.
In a separate bowl, stir together the flour, cocoa, baking soda and salt.
Gradually add the flour mixture, half a cup at a time into the butter mixture and blend until combined.
Use a small cookie scoop, and drop dough onto the prepared baking sheets, 12 cookies per sheet, and bake 8 to 10 minutes.
Cool on a baking rack (don't frost while warm!