Add sugar and vegetable oil to a mixing bowl and cream together. Stir in cocoa powder.

Add eggs, 1 at a time, mixing between each. Stir in vanilla.

In a separate bowl, mix together flour, cocoa powder, baking powder and salt. Add the dry ingredients to the wet, stir until fully combined and no clumps appear.

Cover and chill in the refrigerator for at least 4 hours, up to overnight.

Preheat oven to 350 degrees F. Add powdered sugar to a bowl.

Roll dough into balls. Coat with powdered sugar. Place on a baking sheet lined with parchment paper or a silicone mat, leaving at least 2 inches between each. Bake for 11 to 13 minutes.

Remove from oven, let rest for a few minutes and transfer to a wire rack to completely cool. Store in an air-tight container.