In a large bowl, mix together cocoa powder, sugar, and oil until well blended.
Beat in eggs one at a time, then stir in vanilla.
In a separate bowl, combine flour, baking powder, and salt. Gradually add to the cocoa mixture.
Cover and chill the dough for at least 3 hours (or overnight if you’re a planner).
Preheat oven to 350°F (175°C). Line baking sheets with parchment paper.
Roll dough into 1-inch balls and coat each in powdered sugar.
Place on baking sheet about 2 inches apart.
Bake for 10-12 minutes. They should look a little underdone in the middle—they’ll finish setting as they cool.
Cool for 5 minutes on the pan before transferring to a wire rack.