In a large mixing bowl, stir together both cocoa powders, sugar and vegetable oil, until smooth.
Mix in eggs and vanilla extract. Stir until well blended.
Add flour, baking powder, and salt. Mix well.
Cover with plastic wrap or foil and refrigerate 6 hours or overnight. This will allow dough to set and will be easier to handle.
Preheat your oven to 325°F and line a baking sheet with parchment paper
Pour powdered sugar into a small bowl and set aside
Using a tablespoon, scoop out dough and roll it to a smooth ball
Roll dough ball in the powdered sugar to coat it completely.
Place each dough ball onto the baking sheet about 1.5" apart.
Bake for 10 to 12 minutes. Do not over bake. Cookies should still look a little wet in the cracks.
Remove from oven and allow to cool 2 minutes on pan before transferring to cooling rack.
Store in airtight container for up to one week.