5 ounces of semisweet or bittersweet chocolate, chopped
Transfer pan to a wire rack and let cool to room temperature, about 2 hours.
Stir in the milk, melted butter and vanilla to the flour mixture. Mix until smooth. Pour the mixture into an ungreased 8 inch baking dish. (I used a 9 inch square.)
In separate bowl, mix the remaining white sugar (1/2 cup), the brown sugar and remaining 4 tablespoons of cocoa. Sprinkle this mixture evenly over the batter.