Thaw cool whip, but it still needs to be really cold. I usually will thaw it in the refrigerator the day before I make the pie.
In double boiler melt broken chocolate pieces in double broiler(slowly and stirring often.
Place cold cool whip in large bowl. Pour chocolate in with cool whip. Fold chocolate into cool whip, dont over mix so you will get little chunks of chocolate. You can also fold in nuts at this point if desired.
Refrigerate until firm, usually 1-2 hours. If I'm in a hurry I will simply place it in the freezer for a while.
Garnish with nuts and chocolate shavings. I use one or two squares from the hershey bar to do this.