Preheat the oven to 180C/350F/Gas 4, with a shelf placed in the lower third of the oven.
Place a large square of aluminium foil on a flat surface. Place the springform tin in the middle of the foil. Gently fold up the foil around the sides of the tin. Take care to do this gently so that you don't create any holes in the foil (the idea is to create a waterproof skin around the tin). Press the foil around the edges of the tin. Place a second large square of foil underneath the tin, and repeat. Gently crimp the top of the foil sheets around the top edge of the pan. Make sure no water can get in as this would ruin the crust.
In a food processor, pulse the biscuits and melted butter until finely ground and combined.
Put all but three tablespoons of the crumbs in the bottom of the springform tin. Gently press down the crumbs using your fingers, until you have an even layer at the bottom of the pan, with just a slight rise along the inside edges of the tin. Use the reserved crumbs to fill in any holes or uneven patches.
Bake for 10 minutes. Remove from the oven and set aside to cool for approximately 10 minutes.
Reduce the oven temperature to 160C/320F/Gas 3.
To make the filling, add the cream cheese to the bowl of a freestanding mixer. Add the soured cream, double cream, sugar and eggs. Mix on a medium speed for 5-6 minutes until smooth, soft and creamy. Mix in the vanilla pod seeds. (Remember to scrape down the sides of the mixer bowl, and scrape up any thicker bits of cream cheese that have stuck to the bottom of the mixer that the paddle attachment has failed to incorporate.)
For the topping, in a saucepan gently heat the raspberry jam with 120ml/4fl oz water. Stir to form a smooth liquid. Strain the liquid through a fine sieve to remove any seeds. Set aside.
To cook the cheesecake, place the foil-wrapped springform tin in a large, high-sided roasting tin. Fill a kettle with water and set it to boil.
Pour the cream cheese filling into the springform tin over the biscuit base. Smooth the top with a spatula or the back of a spoon.
Place the roasting tin - with the springform tin sat in it - in the oven, on a low shelf.
Carefully pour the boiling water into the roasting tin (take care not to burn yourself on the hot oven), until the water reaches halfway up the side of the springform tin. (Alternatively, you can add the water before putting the tin in the oven - whichever is easier for you.)
Bake for 1½ hours, or until just set.
Turn off the oven and open the door slightly. Leave the cheesecake in the oven to cool very slowly for an hour (this gentle cooling will help prevent the cheesecake surface from cracking).
Cover the top of the springform tin with foil, so that it doesn't actually touch the cheesecake. Chill in the fridge for a minimum of four hours, or overnight.
Take the cake from the fridge and remove the foil from around the tin. To remove the cheesecake from the tin, carefully run a pallet knife around the edge of the cheesecake. Open the springform latch, ease open the tin and carefully lift it away. You can serve the cheesecake on the base of the tin, but, if you wish to remove it, carefully slide a pallet knife under the cheesecake to loosen it from the tin, then slightly lift one edge of the cheesecake and slide it onto a serving plate.
To serve, decorate the top of the cheesecake with fresh raspberries covered in the topping.