Using an electric beater or a wooden spoon cream together the butter and the sugars..
Beat in the egg, vanilla and salt.
Combine flour, cocoa and baking soda in a separate bowl, and add to the wet mix.
Gently combine until a sticky dough form. If using chocolate chips, mix them in now.
Using a spoon, ice cream scoop or your hands, drop balls of dough onto an ungreased cookie sheet. Bake at 350F for 8-10 mins.
Remove from oven and let the cookies sit on the baking sheet for a minute or so. Gently remove and transfer onto a cooling rack. The cookies continue to cook if left on the hot sheet.