Preheat the oven to 160 C. Line the base and grease the sides of a 22cm spring form cake pan.
Combine the biscuit crumbs and melted butter.
Press the mixture into the base and sides of the cake pan.
In a food processor beat the cream cheese and caster sugar until well blended, add eggs, one at a time and beat well. In a separate bowl mix together the melted
chocolate and sour cream. Pour the cream cheese batter into the biscuit
base and then pour over the chocolate mixture in a swirling pattern. Bake
for 45 minutes, remove from oven and leave to cool before removing tin.
Chill well before serving.