Heat oven to 350 degrees.
Combine flour, cocoa,baking soda and salt. Stir and set aside.
Using a mixer combine the butter and sugar until creamed. Add eggs one at a time stirring after each addition. Stir in vanilla. Add flour mixture a little at a time until completely incorporated.
Wrap the dough in plastic and chill until firm, 1-2 hours.
Roll the dough into 1 1/2 inch balls and roll in sugar to completely coat.
Bake for 11-12 minutes until set in the middle. Move to a cooling rack after 1-2 minutes.