To make the caramel, heat the cream until almost boiling. Place the sugar and water in a deep, heavy bottomed saucepan, bring to the boil and cook, swirling the pan, NOT stirring, until the sugar dissolves and the colour changes to amber. Remove from the heat and immediately pour in the hot cream - be careful as the caramel will bubble ferociously and rise up in the pan. When the bubbling subsides, add the butter and whisk until smooth then whisk in a generous pinch of salt. Set aside to cool.

To make the gingersnap base, place the gingersnaps and ground ginger in a food processor and blitz to fine crumbs, add the melted butter and pulse until the mixture resembles wet sand. Grease a 15cm/6in round deep springform cake tin. Tip the biscuit crumbs into the tin, spread them evenly across the base and press down firmly. Place in the fridge to set while you make the cheesecake.

Whisk the cream cheese until smooth then whisk in the sugar. Whisk in the eggs one at a time, beating well after each addition; finally mix in the sour cream and ground ginger. Divide the mixture in half; whisk the melted chocolate into one half and 60g of the cooled caramel into the other. Place the remaining caramel in the fridge.

Wrap the outside of the cake tin in a double layer of tin foil making sure that it comes just above the top of the tin and there are no cracks or tears in it that water could seep through. Put the kettle on and position a rack in your slow cooker – either a metal one or a bamboo steamer tray will work and failing that you can make one by scrunching a long strip of tin foil into a rope and shaping it into a flat coil, make sure that the cake tin sits level on top of it.

Alternate poring the two cheesecake mixtures into the tin so that you end up with a marbled effect. Place the tin on top of the rack in the slow cooker and pour in enough boiling water so that it comes halfway up the sides of the tin. Place the lid on the slow cooker and cook on high for 2 hours without opening the lid; when the cheesecake is cooked it should be set but still have a bit of a wobble in the centre. Switch the slow cooker off, replace the lid and leave the cheesecake in there for another hour.

Move the cheesecake to a wire rack, removing the tin foil. Carefully run a knife around the edge then leave to cool in it's tin until it reaches room temperature, Cover and refrigerate overnight.

When you are ready to serve, carefully un-mould the cheesecake and slide it onto a serving platter. Gently warm the leftover caramel until it is pourable then drizzle it over the top of the cake before slicing.