In a medium bowl, whisk together the flour, cocoa powder, baking powder and salt until combined.  Set aside.

In the bowl of a stand mixer, add the granulated sugar and oil. Beat on medium-high speed for 2 minutes, or until the mixture is light and fluffy.  Add in the eggs and vanilla, beating on medium-low speed until combined.  Then gradually fold in the flour mixture, and beat on medium-low speed until combined.

Form the dough into a large ball, and place it on a large sheet of plastic wrap.  Wrap the plastic around it so that it is sealed tightly.  Refrigerate for at least 2 hours (or up to 24 hours) until the dough is chilled completely through.

Once you’re ready to bake the cookies, preheat the oven to 350°F.  Line a large cookie sheet with parchment paper.  Fill a small bowl with the powdered sugar.

Remove and unwrap the dough.  Then form the dough into 1-inch round balls.  Dip each dough ball in the powdered sugar until it is completely covered on all sides, and then place them least 2 inches apart on the prepared baking sheet.

Bake for 10 minutes.  Then remove the baking sheet from the oven, and let the cookies cool on the baking sheet for 3 minutes.  Transfer the cookies to a wire rack, and let them cool until they reach room temperature.

Serve immediately, or store in a sealed container for up to 5 days, or freeze for up to 3 months.