Beat cream until stiff, then add sugar to taste and vanilla. Beat egg white in separate bowl until stiff peaks form, then fold into cream. Place cream mixture into pastry bag fitted with star tip. Arrange meringue(s) on serving platter and pipe chestnut puree in bird's nest shape around edge of meringue. Pipe cream mixture in center, piling it high. Sprinkle grated chocolate over whipped cream and chill until serving time.