Cut the vanilla pod lengthways, scrape out the pulp and set aside. Boil the pod with liqueur, 50ml water and 25g sugar and steam the fruit in it for 5 minutes. Cover and chill the whole thing.
Mix the vanilla pulp with the vanilla sugar, remaining sugar, mascarpone, yogurt and lemon zest. First distribute the crumbled biscuits in 4 glasses, then 1-2 tablespoons of cream, then the compote, the remaining cream and finally sprinkle with the nuts. Garnish with mint if necessary.