In a bowl, combine wafer crumbs and butter. Press onto the bottom and 1 in. up the sides of a greased 9-in. springform pan. Refrigerate.
In a saucepan, sprinkle gelatin over milk; let stand for 1 minute. Cook and stir over low heat until gelatin is dissolved. Cut four candy bars into quarters; add to gelatin mixture. Cook until candy bars are melted and mixture is smooth. Remove from heat; set aside.
In a bowl, beat cream cheese and sugar; add gelatin mixture and vanilla. add cream; beat on high speed for 4 minutes. Pour into crust. Refrigerate for at least 4 hours or until firm. Slice or chop remaining candy bar for garnish.