Preheat the oven to 350°F and spray a 13 x 9 inch baking dish with cooking spray. In a small mixing bowl, cut the butter into the flour, then add the pecans. Press firmly onto the bottom of the baking dish.
Bake for 22-25 minutes until lightly golden. Cool completely.
To assemble: In a medium mixing bowl, whip together both cream cheese, powdered sugar and vanilla until creamy and smooth. Fold in one 8 oz whipped topping by hand. Spread over the cooled crust.
In the same bowl, whip together both packages of fudge instant pudding mix with 3 cups of half & half or whole milk. Whip until thickened. Spread evenly over the cream cheese layer.
Frost with the remaining whipped topping. Sprinkle the top with grated chocolate.
Chill for at least 4 hours before cutting.