Preheat the oven to 180°C/fan 160°C/gas 4. Line the base of a 23-24cm springform cake tin with baking paper. For the base, melt the butter in a medium pan, then stir in the crushed biscuits and demerara sugar. Spoon into the tin and press onto the base (not up the sides) in a thin, even layer. Bake in the middle of the oven for 10 minutes, then remove and leave to cool
Increase the oven temperature to 240°C/fan 220°C/gas 9
For the topping, grease the sides of the tin with a little butter. 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 200g caster sugar, flour, followed by the eggs, one at a time, then the yolk. Stir in 200ml soured cream
Pour the cheesecake mixture into the tin, bake for 10 minutes, then lower the temperature to 110°C/fan 90°C/gas ¼ and bake for a further 30-35 minutes until just set but still quite wobbly in the centre. Turn off the oven, open the door slightly and leave the cheesecake inside to cool
Once the cheesecake cools down decorate with passion fruits and nectarine
