Preheat the oven to 350 degrees and line a baking sheet with parchment paper for easy clean up.
In a mixing bowl, cream together butter, shortening, and sugars. Add the egg and vanilla and blend well.
In a separate bowl, whisk remaining dry ingredients - flour, cocoa, baking powder, and baking soda. Slowly pour into wet ingredients and mix.
Scoop dough, about 2 inch rounds, onto the parchment paper and bake for 12-14 minutes or just until the tops no longer look wet. Don't overbake! Remove from the oven, sprinkle with powdered sugar and allow to cool before eating.