Beat the cocoa powder, granulated sugar, and oil in a large bowl on medium speed until shiny and smooth.
Beat in the eggs one at a time, then mix in the vanilla extract.
Whisk the flour, baking powder, and salt in a small bowl. Add to the chocolate mixture and mix on low speed until just combined.
Cover the bowl and chill the dough in the fridge for at least 4 hours, or overnight.
Heat the oven to 350°F (175°C). Line two large baking sheets with parchment paper. Pour the powdered sugar into a small bowl.
Scoop the cold dough and roll into 1 inch balls. Keep the remaining dough in the fridge.
Roll each ball in powdered sugar until fully coated. Place 2 inches apart on the baking sheets.
Bake for 10 to 12 minutes, until the edges are set and the centers are puffed but still a little wet.
Cool on the pan for a few minutes, then move to a wire rack to cool completely.