Grease and line an 8 inch (20cm) springform cake tin and preheat the oven to 350°F (175°C). Make sure that the cream cheese is at room temperature to ensure a smooth finish.

Place the biscuits in a plastic bag and bash with a rolling pin until completely crushed. Melt the butter gently in a saucepan, then mix the two together and press into the base of the tin. Bake the base for 10 minutes, then allow to cool.

Turn the oven up slightly to 400°F (200°C). Mix the sugar and cornstarch together, then using an electric mixer, slowly beat in the cream cheese until smooth. Add the eggs and beat well before adding the sour cream and vanilla extract.

Stand the tin on a couple of sheets of aluminium foil and fold up around the tin, wrapping it so that no water can get in. Spoon the mixture onto the base and smooth the surface. Stand the cheesecake in a baking tray and carefully pour water around it. Bake for 40 to 45 minutes or until golden brown. If the top starts to get too brown, cover loosely with foil. Allow to cool completely before serving.