In a large mixing bowl, combine the cocoa powder, granulated sugar, and vegetable oil. Mix until well blended.

Beat in the eggs, one at a time, and then stir in the vanilla extract.

In another bowl, whisk together the flour, baking powder, and salt.

Gradually add the dry ingredients to the wet ingredients, mixing until a dough forms.

Cover the dough with plastic wrap and refrigerate for at least 4 hours or overnight.

Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.

Scoop tablespoon-sized portions of the chilled dough and roll them into balls.

Roll each ball in powdered sugar until completely coated.

Place the coated dough balls onto the prepared baking sheet, about 2 inches apart.

Bake in the preheated oven for 10 to 12 minutes, or until the cookies have spread and the tops are cracked.

Allow the cookies to cool on the baking sheet for a few minutes before transferring them to a wire rack to cool completely.