BASE: Combine crumbs and margarine; press onto bottom of 23 cm springform pan. BODY: Combine 3 packages cream cheese and sugar, mixing at medium speed on electric mixer until well blended. Add eggs, one at a time, mixing well after each addition. Blend in sour cream and vanilla; pour over crust. Combine remaining package cream cheese and melted chocolate, mixing at medium speed on electric mixer until well blended. Add preserves; mix well. Drop rounded measuring tablespoonfuls of chocolate cream cheese batter over plain cream cheese batter; do not swirl. Bake at 325, 1 hour and 20 minutes. Loosen cake from rim of pan; cool before removing rim of pan. TOPPING: Melt chocolate pieces with whipping cream over low heat, stirring until smooth. Spread over cheesecake. Chill. Garnish with additional whipped cream, raspberries and fresh mint, if desired.