In electric mixer, cream together butter, granulated sugar, brown sugar, and salt. Mix in eggs and vanilla. Mix in cocoa powder. (You may want to stir it in a bit by hand to get it started so the cocoa doesn't go flying everywhere.)
In a separate bowl, whisk together flour, baking powder and baking soda. Gradually fold into butter and cocoa mixture. Fold in chocolate chips and crushed OREOS. Form into balls; chill in refrigerator.
While dough is chilling, preheat oven to 350 degrees.
Roll balls in black sanding sugar. Place on ungreased baking sheet. Bake about 12 minutes. Let stand on cookie sheet one minute; transfer to wire cooling rack.