In medium bowl, combine flour, cocoa powder, baking soda and salt, set aside.
In KitchenAid (or with hand-mixer) cream together butter and sugars.
Add vanilla and beat in eggs, one at a time, pausing after each addition to scrape down sides of bowl with spatula.
Gradually add flour mixture to butter mixture, pausing periodically to scrape down the sides of the bowl.
Chill dough for at least 30 minutes.
Preheat oven to 375F
Roll Tablespoons of cookie dough into balls and bake at 375F for 6-7 minutes.
Immediately upon removing from oven, press gently down on cookies with the back of a spoon to flatten. Allow to cool on pan.
Allow cookies to cool completely before filling with cookie dough.