Preheat the oven to 350 degrees. Line two baking sheets with baking mats or parchment paper.
In a bowl, whisk together the flour, cocoa powder, salt, and baking soda. Set aside.
In a large, microwave-safe bowl, melt the butter. Whisk in the sugar and brown sugar until the sugar starts to melt a little. After the butter has cooled slightly, add the egg and egg yolk and whisk until almost smooth. Stir in the vanilla extract.
Add the dry ingredients to the butter mixture and stir until combined. Stir in the chocolate chips.
Use a 2 tablespoon (or however big you like your cookies) cookie scoop to scoop balls of dough onto the baking pans, leaving a bit of space in between each cookie.
Bake for 11-13 minutes (the cookies will be done when the edges are just set).