Step 1

Heat the oven to 200C/fan 180C/gas Lightly butter and line the base and sides of a 23cm springform cake tin with  baking paper.

Step 2

To make the base, put the biscuits (keeping aside 2 for decoration) into either a food processor, and whizz, or into a ziplock bag and use a rolling pin to crush the biscuits into fine crumbs. Tip the crumbs into a bowl and then pour in the butter, stirring together to evenly mix. Put this mixture into the cake tin and use the base of a glass to compact the crumbs firmly into an even layer, also pressing it slightly up the sides of the tin. Bake for 10-15 minutes or until lightly browned. Put aside to cool.

Step 3

To make the cheesecake filling, put all of the ingredients into a large bowl and use electric beaters to mix until smooth. Pour the mixture into the tin and gently level out. Wrap a wide sheet of foil around the base and sides of the tin and put into the oven, sitting it inside a roasting tray. Pour boiling water into the tray so that it comes about halfway up the sides.

Step 4

Bake for 15 minutes then reduce the temperature to 140C/fan 120C/gas 1 and bake for 1 hour 15 minutes-1 hour 20 minutes or until set around the sides of the cake but with a gentle wobble in the middle. Turn the oven off but leave  the cheesecake inside for 2 hours to cool down slowly, then remove and cool fully at room temperature. Once cooled, put into the fridge overnight to chill and set completely.

Step 5

When ready to serve, spoon the biscuit spread evenly over the top of the chilled cheesecake.

Step 6

To finish, put the double cream and vanilla in a large bowl and whisk to soft peaks. Add the soured cream and fold to combine. Dollop the cream onto the cheesecake and top with the reserved biscuits, crumbled into small pieces.