Mix cake mix (dry), butter and nuts together and press into 9 x 13 inch cake pan. Bake at 350 degrees for 15 minutes. Cool. Mix cream cheese and powdered sugar together and spread over cooled crust. Cover with 1/2 the Cool Whip.
Mix pudding with milk and spread over Cool Whip layer and top with the rest of the Cool Whip. Sprinkle with chocolate shavings or chocolate chips.