Preheat the oven to 180ºC/350ºF/gas 4, and grease and line the bottom and sides of a 24cm springform cake tin. Mix the biscuits and butter in a bowl, press into the base of the prepared tin and cook for 10 minutes. Then remove from the oven and allow to cool. Turn the oven up to 200ºC/400ºF/gas 6. Combine the sugar and cornflour in a bowl. Add the cream cheese and beat, ideally with an electric whisk, until creamy. Add the eggs and beat well. Gradually add the cream, beating until smooth, then beat in the vanilla seeds or extract, cinnamon, lemon and orange zest. Pour the mixture on to the biscuit base, and gently shake it to level out the surface. Put the cheesecake in the centre of the oven and bake for 40 to 45 minutes until the top is golden brown and the filling has set around the edges. (A piece of foil over the top will stop it browning too much.) Let it cool at room temperature and serve after 2 or 3 hours, or, for a slightly firmer texture, place in the fridge to chill.
Before serving, put half the blackberries in a pan with a crumbled bay leaf, sprinkle over the sugar and add a splash of water. Put on a low to medium heat and simmer gently for 10 minutes. Push through a sieve into a bowl, add a tablespoon of port or cassis, cool. Add the remaining berries just before serving, mix gently to coat the berries in the sauce. Spoon over the top of the cooled cheesecake and stud with bay leaves for effect.
For the Blackberry topping