In a mixing bowl combine the cocoa powder, white sugar and vegetable oil-- you can mix by hand or in a stand mixer. Once combined, add the eggs and vanilla extract and mix until evenly combined.
In another bowl combine the all purpose flour, salt, and baking powder.
Spoon in the flour into the wet mix until fully combined. Whatever you are using (hand or stand mixer) don't over mix it.
Cover the bowl with the cookie dough and refrigerate for at least 5 hours (I left it overnight and baked in the morning.)
Preheat oven to 350 F. Line a baking sheet with parchment paper. Measure out small ball of dough, 1.5 t-2 inches balls. Roll the dough into balls with lightly oiled hands. Roll each ball in powdered sugar before placing onto baking sheets.
Bake for 10-12 minutes. Let cool slightly before transferring the cookies to a cooling rack to finish cooling.