Bring the cream cheese and cream to room temperature before you begin. I usually take them out of the fridge a good couple of hours before I start.
Crush the biscuits in a food processor.
Melt the butter and stir it through the crushed biscuits.
Line a loose bottomed cake tin with greaseproof paper. Press the mixture into the base of the tin, pressing down firmly with your fingers. I used a 20cm (8 inch) non-stick tin. Refrigerate while you prepare the topping.
To make the topping:
In a medium bowl, lightly whip the cream until just before soft peaks form. Over-whipping the cream can make your cheesecake grainy so stop before it gets too stiff.
Place the water in a small bowl and sprinkle over the gelatine. Leave to swell for 10 minutes.
In a large bowl beat the cream cheese and sugar for 4-5 minutes until very smooth and soft.
Place a pot of water on the stove and heat it until almost boiling. Put the white chocolate in a bowl big enough to sit over the pot without touching the water, and leave it to melt for a minute or two. Stir gently until you have a nice smooth bowl of melted chocolate.
Place the bowl containing the gelatine over the pot and stir until the gelatine has melted.
Stir the gelatine through the cream cheese and sugar mixture.
Stir the white chocolate into the cream cheese mixture.
Gently fold the cream through the cream cheese, then pour the mixture into the cake tin containing the chocolate biscuit base. Smooth the top with a spatula.
To marble the top:
Melt the dark chocolate using the same method for melting the white chocolate. Dip a teaspoon into the chocolate, and drop small blobs of chocolate all over the top of the cheesecake.
Take a chopstick, skewer or fork and gently swirl the dark chocolate through just the very top of the cheesecake until you are happy with the effect.
Refrigerate the cheesecake for at least 8 hours or, even better, overnight.
To remove the cheesecake from the cake tin:
Take the cheesecake out of the fridge and let it sit at room temperature for 20-30 minutes. Take a kitchen sponge or flannel and run it under hot water for a couple of minutes. Wring out the water then hold it against the outside of the cake tin for a few seconds to lightly soften the edges of the cheesecake. Repeat this process until you've worked your way right around the tin. Gently press the bottom of the cake tin and the cheesecake should slide out. Transfer to a serving plate. To remove the bottom of the cake tin, and the greaseproof paper, carefully slide a thin spatula between the paper and the biscuit base, and gently work the cheesecake off the paper and on to the plate.
Cut with a hot knife into 8-12 pieces.
Notes
Don't be tempted to use spreadable or low-fat cream cheese for this cheesecake - they simply won't give you the same gorgeous creamy texture or set quite as well.
Recipe by The Fare Sage at https://www.thefaresage.com/white-chocolate-cheesecake/