1 Add the sugar to 125 ml water in a pan and bring to the boil. Simmer for 3-4 minutes and leave to cool.
2 Put this syrup in a mixer with the peach flesh, lime juice and schnapps and blend to a fine purée. Beat the egg whites and fold into the peach purée. Finish in an ice cream maker or pour into a flat container and freeze for at least 4 hours, stirring with a fork every 30 minutes to get a smooth sorbet.
3 Serve as soon as the sorbet begins to harden. Alternatively, keep in the freezer until needed and remove from the freezer 20 minutes before serving, giving it a thorough stir.
4 Meanwhile, put a handful of nice-looking raspberries to one side for garnish and purée the remainder with the sugar and vanilla extract. Press the sauce through a sieve if desired, and chill until required.
5 Make scoops of peach sorbet and arrange on plates with the raspberry sauce and the remaining raspberries. Serve with warm chocolate cake if desired.