Line unpricked pastry shell with a double thickness of heavy-duty foil. Bake at 450 for 8 minutes. Remove foil; bake 5 minutes longer. Cool on a wire rack.
In a saucepan combine sugar and cornstarch. Stir in the raspberries, bring to a boil over medium heat. Boil and stir for 2 minutes. Remove from the heat; cool for 15 minutes. Spread into shell; refrigerate. In a mixing bowl, beat cream cheese, sugar and vanilla until fluffy. Fold in whipped cream. Carefully spread over raspberry layer. Cover and refrigerate for at least 1 hour.
Melt chocolate and butter; cool for 4-5 minutes. Pour over filling. Cover and chill for at least 2 hours. Store in the refrigerator.