Whipped cream (optional) To make crust, crush wafers. Add melted butter to make crumbly dough. Press into bottom of 23 cm springform pan. Set aside. To make filling, melt butter in top of double boiler over hot water. Add chocolates and heat until melted, stirring until smooth. Beat cheese until creamy. Add vanilla and whipping cream. Stir in chocolate mixture. Beat eggs with sugar and slowly beat into chocolate mixture. Turn into crust and bake at 180ºC 40 to 45 minutes, or until cake puffs slightly in center. Cool, then chill thoroughly before unmolding. Serve with whipped cream, if desired.