Mix flour, butter, and nuts until crumbly, press into 9×13-inch pan and bake at 350 degrees for 20 minutes. Cool completely. Beat cream cheese and powdered sugar on high with a mixer until smooth. Fold in half the whipped topping. Spread over cooled crust. Mix the puddings with milk; beat slowly with mixer until smooth (2 minutes). Spread on top of cheese layer. Let stand a few minutes, then spoon remaining whipped topping over top and spread carefully. Sprinkle with grated milk chocolate bar. Cover and refrigerate until ready to serve.