How to Make It
Preheat the oven to 375°. Lightly grease a 9-inch square baking pan and line the bottom with parchment paper. In a small bowl, whisk the flours with the salt. In a medium bowl, using an electric mixer, beat the butter with the sugar at medium speed until light and fluffy, about 3 minutes. Beat in the egg and vanilla. At low speed, beat in the dry ingredients along with the chopped chocolate and cocoa powder. Press the dough evenly into the pan. Bake for about 15 minutes, until set.
Meanwhile, in a medium bowl, mix the coconut flakes and condensed milk. Spoon the topping over the dough and bake for 15 minutes, until the flakes are golden. Transfer to a rack to cool for 5 minutes.
Run a knife around the edge of the pan to loosen the cookie. Carefully turn out the cookie and peel off the paper. Turn it coconut-side up on the rack. Let cool completely before cutting into bars.
The bars can be stored in an airtight container for up to 1 week.