This recipe is best prepared the day before you wish to serve it. Set aside a few raspberries for decoration. Purée the remaining raspberries and press through a sieve. Mix the purée with powdered sugar. Beat the whipping cream until stiff. Mix sour cream, low-fat curd and sugar to form a creamy mixture. Fold the raspberry purée into the whipped cream, pour the mixture into a mould (e.g. a loaf pan) which has been covered with film and allow to freeze for 5-6 hours. On the next day, turn the parfait out of the mould and cut into slices. Decorate with raspberries and peach slices.