CRUST Roll out chocolate cream wafers on wax paper. Mix crumbled wafers, butter and nuts in the bottom of a 10" spring form pan. Using a piece of wax paper, press mixture evenly in the bottom of the pan.
Place pan in refrigerator or freezer while preparing the filling.
FILLING Preheat oven to 350 degrees. In a large bowl beat cream cheese until fluffy. Gradually add sugar. Beat in eggs one at a time until well blended. Stir in chocolate and vanilla. Mix well. Pour on top of prepared crust and bake 50 minutes. Remove from oven. Turn oven off and close door.
TOPPING Combine sour cream, sugar and vanilla. Spread over cheesecake.
Return to oven, but do not reheat oven. Leave in warm oven for 10 minutes with the door closed. Open door and leave cake in oven for an additional 20 minutes. Remove cake from oven. Allow cake to cool on wire rack.
FINAL TOUCH Freeze Hershey bar. When cake is cooled, shave frozen chocolate on top of cake. Refrigerate overnight.