For the crust
2 cups graham cracker crumbs
6 tbsp butter, melted
1 tbsp sugar
For the cake
4 8oz cream cheese
1 cup sugar
1/2 tsp salt
2 tsp vanila extract
4 large eggs, room temperature
1 cup sour cream
3.5 oz dark chocolate, melted
5 oz white chocolate, melted
1. Butter a 9″ spring sided cake tin (sides should be 2 3/4″ high). Double wrap the outside of the springform pan with aluminum foil.
2. Combine the digestive biscuit crumbs, the sugar and salt together in a large bowl and then add the melted butter, mix until thoroughly combined.
3. Add the moistened crumbs to the spring sided tin and create an even layer across the base of the tin and approximately half way up the sides of the tin.
4. Place the tin into the freezer to allow the crust to begin to set and turn on the oven to preheat at 340. Once the oven is heated, place the tin on the center shelf and allow to prebake for 10 minutes. After the crust has prebaked remove from the over and set aside to cool whilst making the cheesecake batter.
5. Beat cream cheese at medium speed until smooth. Add in sugar and salt, and continue to beat until mixture is light and creamy.
6. Add in vanilla extract. Then add in the eggs, one at a time, beating for about 1 minute after each addition.
7. Pour 1/3 of the batter into the dark chocolate mixture. Add the remaining batter into the melted white chocolate. Mix both quickly until combined.
8. Pour 1/3 of the white chocolate batter into the cooled springform pan. Add in dollops of the dark chocolate batter at random spots. Pour in the remaining white chocolate batter. Drop in the rest of the dark chocolate batter. Take a fork or a knife and swirl the batter gently.
9. Put the springform pan on to the roasting pan in the oven. Pour enough boiling water into the roasting pan until it comes halfway up the sides of the springform pan.
10. Bake the cheesecake for about 1 hour and 30 minutes. Turn off the oven and prop open the oven door slightly. Leave the cake in the oven for half and hour or so. Take down and let it cool completely before refrigerating for at least 4 hours.
