1. Crush the biscuits in a blender or food processor, then mix with the melted butter. Spoon into a lightly greased 20cm spring-release cake tin and spread evenly. Chill while preparing the filling.
2. Put all the filling ingredients in a food processor and pulse briefly until smooth. Spoon over the biscuit base and bake at 150°C / fan oven 140°C / 300°F / Mark 2 for 1 ¼ hours. At this stage the cheesecake will still be slightly soft in the middle.
3. Turn off the heat but do not open the door. Leave the cheesecake to cool completely in the switched-off oven, for 3-4 hours. It will continue to firm up during this time.
Refrigerate until you are ready to serve.