In a medium-sized mixing bowl, combine the cocoa powder, white sugar, and brown sugar. Mix well to incorporate.
Add canola oil and beat in the eggs one at a time until well combined. Blend in the vanilla extract and mix until fully incorporated.
Sift flour, baking powder, and salt over the mixing bowl. Fold in the dry ingredients into the wet mixture just until a dough forms (do not over beat).
Wrap the bowl with plastic wrap and chill for at least 3 hours or overnight.
Preheat the oven to 350°F / 180°C when ready to bake. Line baking trays with parchment paper or baking paper.
Using a measuring spoon (1 tablespoon) or an ice cream or cookie scooper, scoop 1 tablespoonful of dough and roll into balls with the palm of your hands.
Put granulated sugar in one small bowl and confectioners' sugar or icing sugar in another bowl. Lightly coat each ball of dough in the granulated sugar then coat generously with confectioners' sugar.
Place cookies on the prepared baking sheet, making sure there is enough space between them.
Bake for 10 minutes in a preheated oven. Note: The cookies will be soft when they come out of the oven, but they will harden as they cool.
Allow to cool for 5 minutes on the baking sheet before transferring to wire rack to cool completely.
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