Preheat the oven to 350°F and spray a 13x9 inch baking dish with cooking spray.
In a small bowl use a pastry blender to cut the butter into the flour until it resembles cornmeal. Add the pecans mix to combine. Press firmly onto the bottom of the baking dish.
Bake for 22-25 minutes until lightly golden. Cool completely.
Assemble: 1st Layer - In a medium mixing bowl use a mixer to whip together cream cheese, powdered sugar and vanilla until creamy and smooth. Fold in one 8 oz whipped topping by hand. Spread over the cooled crust.
2nd Layer - In the same bowl whip together both packages of fudge instant pudding mix with 3 cups of half and half or whole milk. Whip until thickened. Spread evenly over the cream cheese layer.
3rd Layer - Frost the top with the remaining whipped topping. Sprinkle the top with grated chocolate.