1.Grease a 12.5cm x 35cm loose-based flan tin.
2.Process biscuits until fine. Add butter; process until combined. Press mixture over base and sides of flan tin. Refrigerate 30 minutes.
3.Preheat oven to 150°C.
4.Break chocolate into a small heatproof bowl; place bowl over a small saucepan of simmering water, stirring, until chocolate is smooth (don’t let water touch base of bowl). Cool.
5.Split vanilla bean lengthways; scrape out seeds (keep vanilla pod for another use, see notes). Beat cheese, sugar, eggs and vanilla seeds in a small bowl with an electric mixer until thick and smooth. Add cooled melted chocolate and cream; beat until mixture thickens slightly. Pour filling into tin.
6.Bake cheesecake for 30 minutes; cool in the oven with door ajar. Refrigerate 2 hours.
7.Just before serving, place extra chocolate in a small heatproof bowl over a small saucepan of simmering water; stir until smooth. Top cheesecake with berries, drizzle with chocolate.
Place the unused vanilla pod in a jar of caster (superfine) sugar to make your own vanilla sugar.Note