Using a mixer, combine the melted butter, brown sugar and granulated sugar.

Add in egg, egg yolks and vanilla, and mix for 1-2 minutes.

Add in the flour, cocoa powder, baking soda and salt. Scrape the sides of the bowl and the bottom really well.

Add the chocolate chips and gently stir by hand; let the dough sit 20 minutes in the fridge.

Preheat oven to 325. Line baking sheets with parchment paper, and scoop cookie dough onto prepared pans, using a two tablespoon cookie scoop.

Bake 10-12 minutes (or less if you like them gooier).

Leave the cookies on the hot baking pans for 5-7 minutes, or until you can remove them without falling apart. Place onto cooling racks and cool to room temperature, before storing in air tight containers.