In a big bowl or mixer, combine the cocoa, sugar and vegetable oil. Give it a good mix. Drop the eggs one at a time while mixing. Add the vanilla extract too.
In a separate bowl, sift the flour, baking powder and salt. Also add the espresso powder. Whisk. Pour the flour mixture to the cocoa mixture. Combine well. Cover and chill overnight inside the fridge.
The next day, preheat your oven at 350 degrees F and line 2 baking sheets with parchment paper, set aside. In a bowl, place your powdered sugar.
Using a spoon or a scooper, scoop the chilled dough and roll the dough using your hand into balls, about 1-inch size. Drop the balls into a bowl of powdered sugar and make sure to roll them to totally cover the balls with the sugar. Place on the prepared baking sheets and make sure to make spaces between cookies.
Bake for 10-12 minutes and make sure to allow to cool for a couple of minutes before removing them from the baking sheet and transferring them into the wire rack. Serve and enjoy. Store in an airtight container for a week.