In a medium bowl, mix together cocoa, white sugar, and vegetable oil. Beat in eggs one at a time and stir in the vanilla. Whisk together the flour, baking powder, and salt; stir into the cocoa mixture. The mixture will be wet, a little sticky (which is why we chill) and the consistency of brownie batter. Chill for at least 3 hours.
Preheat oven to 350 degrees F . Line cookie sheets with parchment paper. Roll dough into 1.5 inch balls (size 40 scoop). Roll cookies well in powdered sugar.
Bake in preheated oven for 8 to 12 minutes. This will depend on your oven and how you like your cookies. If you like a fudgy middle you'll be towards 8 minutes (they will look wet but will set up as they cool). If you like a crisper edge you'll cook them for around 12 minutes. Let cookies cool on the cookie sheet for a a couple of minutes before transferring to wire racks to cool.
Notes
Keep the dough chilled in between batches in the fridge. Want to up the chocolate factor. Stir in 1 cup of mini or semisweet chocolate chips into the batter.Source: Allrecipes