Preheat oven to 350 degrees F. In a medium bowl, combine the melted butter, flour, and 3/4 cup nuts. Press mixture into a 9"x13" baking dish. Bake 10 to 12 minutes, or until a firm crust forms and let cool. In a medium bowl, whisk together pudding mix and milk until thickened and set aside.
In another medium bowl, combine cream cheese, confectioners' sugar, and half the whipped topping and mix well. Using a wet table knife, spread cream cheese mixture over top of cooled crust. Spoon chocolate pudding mixture over top of cream cheese mixture then top with remaining whipped topping. Sprinkle remaining walnuts on top. Cover and chill overnight, or at least 6 hours. Refrigerate any leftovers.