In the bowl of a stand mixer, mix together the sugar and oil. Add in the eggs one at a time, mixing until fully incorporated. Stir in the vanilla.
In a seperate bowl, mix together the cocoa powder, flour, baking powder, salt. Slowly add into the wet ingredients, mixing until fully combined.
Cover, and place in the refrigerator for at least 6 hours.
Preheat the oven to 350˚F. Line 2 cookie sheet with parchment paper. Add around 1/4 cup powdered sugar in a small bowl.
Using a cookie scoop, scoop the chilled dough and roll in hands. Roll in the powdered sugar and place on the prepared cookie sheet. Repeat with the remaining dough.
Bake in the preheated oven for 12-14 minutes. Remove from oven and allow to cool on cookie sheet for around 5 minute, then transfer to wire racks to cool completely.