In a large bowl combine pudding mix and powdered sugar. Add half-and-half. Beat with an electric mixer on medium speed until thickened. Fold in whipped topping.
Divide half of the crumbled brownies between 4 large parfait glasses or water goblets. Divide half of the raspberries, ice cream topping, and pudding mixture between the glasses, creating layers. Repeat layers with remaining brownies, raspberries, ice cream topping, and pudding mixture. If desired, sprinkle with cocoa powder. Serve immediately or cover and chill up to 4 hours.