Combine the flour, salt, baking soda, baking powder and cocoa in a medium mixing bowl.
Add the room temperature butter, brown sugar and granulated sugar to a large mixing bowl, or the bowl of a stand mixer.
Use the stand mixer, or an electric hand mixer, to cream the butter and sugar together on medium speed for 2 minutes.
Add the egg, egg yolk and vanilla extract.
Beat on medium speed until combined.
Add the flour mixture and beat until all of the ingredients are combined.
Add the chocolate chips and use a spatula to stir them into the cookie dough.
Roll into golf ball sized balls and place on a baking stone or baking sheet lined with parchment paper.
Place in the oven and bake for 10 minutes.
Baked cookies can be stored at room temperature in a covered container for 4-5 days.
Store any uncooked balls of dough in the refrigerator or freezer in a freezer-safe bag or container. The balls of dough will stay good in the refrigerator for up to 2 weeks and in the freezer for up to 6 months.
When baking the balls of dough from the refrigerator, I recommend placing them on the countertop for at least 30 minutes to come up to room temperature.
When baking the cookies from frozen, I recommend allowing them to thaw in the refrigerator for at least 12 hours. Then follow the recommendation above for baking cookies from the refrigerator.