For the cookies:
Heat oven to 375 F.
Line baking sheets with parchment paper.
In a medium bowl, add flour, cocoa, baking soda and salt; mix until combined.
In separate large bowl, beat butter and sugar with a mixer on medium until light and fluffy, about 2 minutes.
Add egg and vanilla and beat for two more minutes.
Add half of the flour mixture and half of the milk and beat on low until incorporated.
Repeat with remaining flour and milk and beat until combined.
Drop batter on prepared baking sheets in tablespoon clumps, each about two inches apart. Bake for 10-12 minutes each or until pies spring back when pressed gently.
Cool for about five minutes before transferring them to a rack to cool completely.