Preheat oven to 350˚F.
With a mixer, cream together the butter and sugar until light and fluffy.
Add eggs and vanilla to butter mixture. Blend well.
In a separate bowl, combine flour, cocoa, baking soda and salt.
Add flour mixture to butter mixture and mix well. Add chocolate chips.
Drop by tablespoon onto cookie sheet.
Bake for 8 minutes. Do not overbake!