Crush the digestive biscuits and mix with melted butter. Into a cake dish, add the mixture and press to create a solid base. Chill in the fridge for 30 minutes.
In a bowl, combine 200ml of cream, cream cheese, icing sugar, sour cream and vanilla extract and mix until smooth. Add 4 tbsp cherry jam and marble through the mixture. Pour into the cake tin, smooth, and chill for 20 min.
Make ganache by heating 100ml cream and then adding chunks of chocolate and stirring to melt.
Pour ganache over cake, chill for 10 minutes, then add remaining 2 tbsp jam in the middle.