Preheat oven to 350℉

In a large bowl, melt the butter, and once at room temperature, combine with the egg and vanilla. Add in the granulated sugar and brown sugar - whisk until smooth.

In a separate bowl, combine dry ingredients - flour, cocoa powder and baking soda.

Add the dry ingredients into the wet, and mix to combine. 

Form the dough into balls about 1 tablespoon - put in the fridge for 30 minutes (minimum). 

Before baking, take the dough out of the fridge and let it come to room temperature. 

Bake for 12-14 minutes. 

Top with sea salt flakes if desired.