Ingredients

Step by step

1. Preheat the oven to 180°C, fan 160°C, gas 4, and position a shelf in the middle of the oven. Line the base of a round 23cm springform tin (7cm deep) with baking paper.
2. For the biscuit base, melt the butter in a pan then stir in the biscuit crumbs and demerara. Press into the base of the tin in an even layer. Bake for 10 minutes; set aside to cool.
3. Increase the oven temperature to 240°C, fan 220°C, gas 9. Grease the sides of the tin with a little extra butter.
4. For the cheesecake, break the white chocolate into a heatproof bowl over a pan of barely simmering water. Don't let the bowl come into contact with the water, or let the chocolate become too hot. Stir the chocolate as it melts until it's smooth, then remove the bowl and set aside.
5. Scoop the cream cheese into a large mixing bowl and beat with a hand-held electric mixer for 2 minutes until smooth and creamy. Beat in the flour, a pinch of salt and vanilla bean paste, followed by the eggs, one at a time, and then the yolk. Stir in the cooled melted white chocolate and soured cream (or crème fraîche).
6. Pour the cheesecake mixture into the tin and bake for 10 minutes, then lower the temperature to 110°C, fan 90°C, gas ¼, and bake for a further 40 minutes until just set but still quite wobbly. Once cooled, this will set nicely to produce a cheesecake with a soft texture. Turn off the oven, leave the door ajar (wedge it open with the handle of wooden spoon if necessary) and leave it to cool inside the oven. Carefully run a round-bladed knife around the sides of the tin to release the cheesecake and remove the sides of the tin.
7. To decorate, break two-thirds of the plain chocolate into a heatproof bowl and melt as before. Remove the bowl from the heat, add the remaining chocolate and stir until melted. Leave to cool slightly. Pour some of the chocolate into a small piping bag with a fine nozzle and pipe about 16 little Christmas trees onto a tray lined with baking paper. Set aside until firm. Pour the rest of the melted chocolate onto a granite or marble slab or baking tray and spread it out thinly. When it has just set but is still pliable, push a cake or dough scraper through the chocolate to form curls.
8. For the white chocolate mousse coating, melt the chocolate as before. Set aside to cool slightly. Whip the cream cheese until light and fluffy and then stir in the melted white chocolate. In a separate bowl, whip the cream, icing sugar and vanilla extract until beginning to form soft peaks. Fold in the white chocolate mixture. Place the cheesecake on a serving plate and spread the mousse over the top and sides. Decorate the top with the chocolate curls, then press the chocolate Christmas trees around the outside edge. Dust with a little icing sugar.