Set aside 8 to 10 of the raspberries. In a large bowl combine the remaining raspberries, the sugar, and orange peel. Spoon berry mixture into a 1- to 1-1/2- quart compote dish or serving bowl.
In a chilled mixing bowl combine whipping cream and liqueur (if using); beat with chilled beaters of an electric mixer on medium speed until soft peaks form (tips curl). Spoon on top of raspberry mixture. Top the whipped cream with the brownie chunks and the reserved raspberries. Makes 12 servings.