Cream butter, sugar, egg and vanilla until well blended. Combine cocoa and buttermilk (or water) in a separate bowl until smooth.
Add to creamed mixture. Add flour, baking soda and salt, beating just until blended. Stir in chocolate chips. Drop dough by teaspoonfuls onto ungreased cookie sheet. Bake at 350 F for 8-10 minutes or until centers are almost set. Remove from cookie sheet while hot.
