In a medium bowl, whisk together the flour, baking powder, and salt. Set aside.
In a large mixing bowl fitted with the paddle attachment, combine the granulated sugar, cocoa powder, and oil. Beat on medium speed until blended and shiny.
Add the eggs, one at a time, and beat on medium speed until blended.
Beat in the vanilla extract.
With the mixer on low speed, add the flour mixture and beat until just combined.
Cover the bowl with plastic wrap and refrigerate the dough for at least 3 hours, and up to 3 days.
Preheat the oven to 350 degrees. Line two large baking sheets with parchment paper.
Place the powdered sugar in a bowl.
Using a standard cookie scoop (or 2 tablespoons), scoop the chilled dough and then shape into balls. Only make as many balls as will fit on your baking sheet. Refrigerate the remaining dough until ready to bake.
Transfer the dough balls to the powdered sugar and turn to coat.
Place the cookies on the prepared pan, about 2 inches apart.
Bake for 10 to 12 minutes, until the edges of the cookies are firm and the center is puffed up and wet-looking.
Cool the cookies on the pan, on a wire rack, for 5 minutes.
Transfer the cookies to the rack to cool completely.