In a medium bowl, mix together cocoa, vegetable oil and white sugar. Beat in eggs one at a time, then stir in the vanilla. Mix the flour, baking powder and salt into the cocoa mixture. Cover dough, and chill for at least 2 hours.
Preheat oven to 175° C. Line baking sheet with parchment paper. Roll dough into one inch balls. Coat each ball in confectioners sugar before placing onto prepared baking sheet.
Bake in preheated oven for 10 to 12 minutes. Cool into wire racks before serving.
Notes
You could chill the dough in freezer for about 20 minutes if you do not want to wait that long, just like me!
This is not very sweet, so if you prefer sweeter cookies, try adding about 1/4 cup sugar to the cocoa mixture.