CRUST- mix wafer crumbs and butter and press with spoon onto bottom and part way up the sides of 8" or 9" spring form pan.
FILLING- Preheat oven to 350. Blend cream cheese with sugar and eggs. Add (4 oz) melted chocolate, beating until thick and smooth. Pour into prepared crust. Bake for 30-40 minutes or until firm inthe center. Chill 4 hours or overnight.
TOPPING- Stir (4 oz) melted chocolate into sour cream, and spread over top of cheese cake. Chill until firm.