Recipe from Foodnetwork.com : Ellie Krieger
See original recipe here
Ingredients Nonstick cooking spray 6 ounces bittersweet chocolate, coarsely chopped 2 tablespoons unsalted butter 1 cup whole-grain pastry flour (or 1/2 cup each whole-wheat and all-purpose flours) 1/4 cup unsweetened cocoa powder 1/4 teaspoon salt 1/4 teaspoon baking soda 4 large eggs 1 cup packed light brown sugar 1/2 cup plain low-fat yogurt 1/4 cup canola oil 2 teaspoons vanilla extract 3/4 cup chopped walnuts (optional)
Preheat the oven to 350 degrees. Coat a 9-by-13-inch baking dish with cooking spray.
Melt the chocolate and butter in a heatproof bowl set over a saucepan of barely simmering water, stirring occasionally; do not let the bottom of the bowl touch the water.