In a bowl, mix the yoghurt with all the ingredients up to and including kirsch until smooth. Carefully fold in the cream. Layer the sponge and cinnamon parfait in the spring form tin, finishing with parfait, cover and freeze for approx. 3 hrs.
Remove the tin frame, cover the cake with the whipped cream and freeze for about another 2 hrs.
Transfer the cake to the fridge for about an hour before serving, remove the spring form base, slide the cake onto a platter and decorate with pistachios and physalis.