Mix flour, margarine (butter) and walnuts together. Press into a greased 13"x9" baking pan. Bake at 35o*- for 18 minutes; Cool.
Combine cream cheese, powdered sugar, and half of whipped topping. Whip together until smooth. Spread on cooled crust. Mix together pudding, milk and remaining whipped topping until smooth. Spread over cream cheese mixture.
Sprinkle with additional nuts, if desired. Chill several hours before serving. Serves 12-16.