In a large bowl, stir together cocoa powder and white sugar. Add vegetable oil and stir until well blended
Add eggs, one at a time, mixing between additions.
Stir in vanilla extract.
In separate bowl, whisk together flour, baking powder and salt.
Add flour mixture to sugar and oil mixture. Mix well.
Cover with plastic wrap and refrigerate overnight or at least 6 hours.
After chilling the dough, preheat oven to 350°F and line cookie sheets with parchment paper.
Add confectioner's sugar to a small shallow bowl.
Roll dough into balls of about 1-1/2 tablespoons of dough.
Coat each ball in the confectioner's sugar, covering the entire cookie.
Place cookie balls on parchment-lined cookie sheets, about 2 inches apart. Do not flatten as the cookie will flatten as it bakes.
Bake for 12-14 minutes. Remove to cooling rack to cool completely.
Store in an airtight container at room temperature for up to 1 week.
