In a medium bowl, mix together cocoa, white sugar, and vegetable oil. Beat in eggs one at a time, then stir in the vanilla. Combine the flour, baking powder, and salt; stir into the cocoa mixture. Cover dough, and chill for at least 4 hours.
Preheat oven to 350 degrees
Line cookie sheets with parchment paper.
Roll dough into one inch balls with lightly oiled palms. I used a size 50 cookie scoop to portion the dough, a tablespoon or rounded teaspoon would also work depending on what size you like.
Coat each ball in confectioners’ sugar before placing onto prepared cookie sheets. [Alternatively, try other ingredients like cinnamon-sugar or sprinkles.]
Bake in preheated oven for 10 to 12 minutes. Let stand on the cookie sheet for a minute before transferring to wire racks to cool.
Source: https://bittersweetbaker.wordpress.com/2010/10/24/chocolate-crinkle-cookies/