Preheat oven to 350F. Mix together the butter, flour and chopped pecans. Press into a 9 x 13" pan and bake for 15-20 min. Set aside and cool.
In the bowl of a stand up mixer, beat together cream cheese, sugar and 1 cup of Cool Whip. Spread onto top of cooled cookie layer.
Next beat your puddings with 2 1/2 cups milk each, until stiff. Layer on vanilla, then chocolate pudding onto the cream cheese filling. Place the last 3 cups of Cool Whip on next and top with grated chocolate.