Chocolate cheesecake with white chocolate icing

Instructions

1. Mix the crushed biscuits and melted and cooled butter together until everything is well incorporated. Place in a 21-23 cm springform tin and squeeze the mixture flat with the back of the wooden spoon. Then use something flat to make it even. I use the bottom of a cake tin, which is slightly smaller than the springform tin, and press down very hard all the way around so that the biscuit mix is flat and even.
2. Put the cream cheese and icing sugar in a bowl and mix together gently. Melt the chocolate in a heatproof bowl set over a pan of simmering water, making sure the bottom of the bowl does not touch the water, or you can do this in the microwave. Pour a quarter of the chocolate into a jug, add the oil then set aside and keep warm. If you have a microwave the chocolate can be blasted for 20 seconds before it needs to be used again if not, just cover it with a clean tea towel and set it somewhere warm.
3. Now add a large dollop of the cream cheese mixture into the bowl of remaining chocolate and stir well to combine. Add another dollop of cream cheese mixture to the chocolate mixture and stir to combine. Keep adding the cream cheese mixture, one dollop at a time, and mixing it like mad until the chocolate mixture begins to look uniform, smooth and silky.
4. At this point, tip all of the cream cheese mixture into the chocolate mixture and mix together until it is completely incorporated. Tip the mixture on top of the biscuit base and use the back of a large spoon to smooth the top. Press it down well so there are no gaps. Pop the cheesecake in the fridge for about 20 minutes or the freezer for 10 minutes, or until the chocolate top is beginning to firm up a little. It won’t be totally hard, but it will begin to feel a bit tacky.
5. Five minutes before the cheesecake is ready, melt the white chocolate and make sure the jug of milk chocolate is nice and runny.
6. Now remove the cheesecake from the fridge and, acting quickly, pour the milk chocolate over the top of it, spreading it out as you go until the top is completely covered. For a smooth finish, pick up the cheesecake and tilt it back and forth, letting the chocolate run over and cover the cream cheese filling.
7. Now drizzle white chocolate lines across the top about 2 cm apart. The neatest way to do this is by putting the chocolate into a piping bag fitted with a very small nozzle.
8. Place the cheesecake so the lines are running towards you, then take a cocktail stick and drag it from left to right, making lines from left to right 2 cm apart so you have a grid. Using the cocktail stick, drag it from right to left between the toothpick lines that you have just made. You will need to do this quite quickly so the chocolate lines are still runny. Leave the cheesecake in a cool place to set for about 2 hours.
9. Remove springform rim before serving (you can aid this by dipping a knife in warm water and running it around the inside of the tin). Serve in wedges with a drizzle of single cream.