Crust: In small sauce pan melt butter. In medium bowl place flour, add melted butter, and pecans; mix till crumbly. Place in 9 x 13 pan and press down. Bake at 350°F for 15 minutes. Let cool.
Filling: Mix cream cheese, powder sugar and 1/2 tub of whipped topping with mixer, spread over cooled crust.
Mix vanilla pudding according to pkg. directions and spread over cream cheese mixture. Mix chocolate pudding according to pkg. directions and spread over vanilla pudding. Top with remaining whipped topping, sprinkle chopped pecans over whipped topping. Refrigerate for 30-35 minutes before eating.