Preheat oven to 350°. Spray an 8" pan with non-stick spray, add 1 tbsp. flour and turn to coat bottom and sides. Shake out excess flour. Whisk 1/2 cup flour, sugar, cocoa powder, brown sugar, baking soda and salt in a medium bowl. Whisk the chocolate and oil in a large bowl. Add yogurt, egg and vanilla; whisk well. Add flour mixture and stir with a wooden spoon until just moistened, with no white grains visible. Pour into pan. Bake until a toothpick inserted comes out with moist crumbs attached, about 30 minutes. Cool in the pan before turning out and cutting. Dust with confectioners sugar before serving, if desired. To produce the densest, fudgiest brownies, lift the pan about a half inch and then gently drop it back down on the oven rack halfway through baking. Always err on the side of underbaking; the middle should be set, yet a tad wet.
Per serving: 140 cal. 5 g. fat, 2 g. sat. fat, 1 g. fiber