Combine butter and flour; pat into a 13x9 x2 inch baking pan. Bake at 350 for 20-25 minutes or until lightly browned. Cool. In a large mixing bowl, blend cream cheese and sugar on medium speed until smooth. Add half of the whipped topping, beating on low. Spread over crust. In another bowl, beat pudding mixes and milk for 2 minutes on low speed. Let set 10 minutes. Spread over cream cheese layer; let set 10-15 minutes. Cover with remaining whipped topping. Top with pecans if desired. Refrigerate overnight.