Preheat oven to 325 degrees.
In a bowl, sift flour, cocoa powder, baking powder, cinnamon, ginger, and salt. Set aside.
In a separate large bowl, mix oil, sugar and molasses until well blended.
Add eggs and vanilla and mix well.
Add dry ingredients to wet and stir until just mixed.
Fold in sour cream.
Pour batter into a greased 9x9 baking pan for 25 minutes.
Cut into squares and dust with powdered sugar.
