Preheat oven to 350 degrees F. Line cookie sheets with parchment paper. In a large mixing bowl beat butter with an electric mixer on medium speed for 30 seconds. Beat in oil, brown sugar, and granulated sugar until well combined. Beat in egg and vanilla until combined. In a medium bowl whisk together flours, cocoa powder, baking powder, and salt; beat into sugar mixture. Stir in chopped chocolate.
Drop dough by slightly rounded teaspoons 2 inches apart onto prepared cookie sheets. Bake about 12 minutes or just until edges are set. Let cool 1 minute on cookie sheets. Transfer cookies to wire rack to cool. Makes about 36 cookies.