• To prepare my tin, I like to put a square of greaseproof paper over the base on the tin and then close the springform over the paper, so that it's trapped and hangs out over the edges.

Oreo Biscuit Crust

• Preheat oven to 160°C.
• Melt the unsalted butter in the microwave or on the hob. Set to one side.
• In a food processor, blend the Oreos (whole) until they are in a fine crumb. Please don't put your hand into a plugged in food processor.
• Add the melted butter and blitz again until fully combined.
• Press this biscuit crumb into the bottom of your springform tin until it forms an even layer.
• Bake for 10 minutes.

Chocolate Cheesecake

• Prepare your waterbath. Wrap the bottom of your springform in several layers of tin foil to make it water tight. Sit the tin in a large, deep baking tray,
• Melt your chocolate in the microwave in 30 seconds blasts with lots of stirring or over a bain-marie. Set aside.
• In your food processor, blend your cream cheese to make sure it is smooth.
• Add the sugars and cocoa powder and blitz again. Scarp down the sides.
• Add the eggs, egg yolks, sour cream and vanilla and pulse for 20 seconds. You don't want to blitz for too long here, as you'll add air to the eggs, which might cause cracks later.
• Scrap down the sides. Finally add your melted chocolate and blitz again until just combined. Give it a final scrap around the sides with your spatula.
• Remove the bowl from your food processor and pour into your springform tin.
• Place your tin into the large baking tray and put it onto a shelf in your oven. Pour enough hot water into the baking tray so that it comes up about one inch on the side of the springform tin.
• Bake for 1 hour and 10 minutes. It will be wobbly in the centre.
• Remove from the water bath and leave it cool completely before putting it in the fridge for minimum 6 hours, but preferably overnight. Leave it in the springform here.