Prepare and bake brownies in a 13×9 inch pan according to package directions; set aside to cool.
While brownies are cooling using an electric mixer with whisk attachment mix the milk and pudding together for 2 minutes. Add the peanut butter and sugar, and mix until well combined.
After brownies are completely cooled spread the pudding mixture over the top of the brownies.
Place the chocolate and cool whip in a medium size microwavable bowl and microwave for 1 minute stirring every 30 seconds until chocolate is melted and the mixture is thoroughly combined. Spread chocolate mixture over the top and sprinkle with nuts.
Refrigerate and cool for at least one hour before serving.