Mix butter, flour, and sugar together in a bowl with either a fork or your hands. Press down flat in a 9x13 pan. Bake in oven at 350 degrees for 15-20 minutes or until slightly golden brown. Let cool completely. Once cooled, add your pecans.
Mix cream cheese, cool whip, and powdered sugar together. Spread evenly on top of crust.
Mix milk and chocolate pudding together. Let it set up for about 5 minutes, and then spread it evenly on top of the cream cheese layer.
Spread remaining cool whip on stop of chocolate pudding layer. Add remaining pecans.
Grate chocolate bar with a cheese grater. Add on top as final finishing touch.