In a large bowl whisk together flour, 3/4 cup powdered sugar, cocoa, baking powder and salt.

In a small saucepan over low heat mix together canola oil and chopped unsweetened chocolate. Cook until melted, stirring constantly. Remove from heat. Let cool for 10 minutes.

Add brown sugar, corn syrup and vanilla to the melted chocolate and stir until fully combined.

Whisk in the egg whites until everything is well blended.

Pour into flour mixture, stirring until just combined.

Cover, and refrigerate for at least 2 hours, can be overnight.

Preheat oven to 350º F.

Roll dough into 1 inch balls. Roll balls through the remaining 1/2 cup powdered sugar. Place on a baking sheet lined with a silpat or parchment paper.

Bake for 10 minutes, or until tops are cracked and almost set.

Cool for 5 minutes on the pan before removing to a wire rack.