Caramelised white chocolate cheesecake

Method

1. Whizz the biscuits to a crumb in a food processor or bash with the end of a rolling pin in a large bowl. Melt the butter, then mix it into the biscuits along with the cocoa powder. Grease the cake tin with butter, then press the biscuit mixture evenly into the base and up the sides of the tin. Chill for at least 30 minutes.
2. Take half the caramelised white chocolate and melt it (in a microwave in 20 second bursts or over a pan of barely simmering water). Heat the oven to 150°C fan/gas 3½. Put the cream cheese, sugar, soured cream and vanilla in a mixing bowl. Using an electric mixer, beat until well combined. In a separate bowl, beat the cornflour and one of the eggs until smooth, then beat in the remaining eggs. Beat this into the cream cheese mixture, then stir in the melted chocolate.
3. Put the cake tin on a baking tray and fill with the cheesecake mixture. Bake for 1 hour to 1 hour 15 minutes until the top edge of the filling is firm but the centre has a slight wobble. Turn the oven off and leave the cake to cool inside, with the door ajar, for about 2 hours. Once completely cool, chill overnight.
4. About 30 minutes before serving, remove the cheesecake from the fridge.  Gently heat the remaining caramelised white chocolate in a heatproof bowl until almost all melted (in a microwave at 20 second intervals or set over a pan of barely simmering water). In a small pan, heat the double cream and, once steaming, pour this over the chocolate. Stir until fully melted and combined. Spread the caramelised white chocolate ganache over the surface of the cheesecake with a palette knife, creating waves and ridges to add texture. Leave to set before removing from the tin and slicing.