To make the chocolate sponge:
1. Heat your oven to 160°C. Grease a 23cm round loose bottom cake tin and line the base with baking parchment.
2. Break the chocolate into chunks and place into a pan with the water and butter. Melt over a gentle heat, stirring occasionally until the chocolate and butter have melted and you have a smooth mixture. Leave to one side to cool.
3. Sieve the flour and baking powder together.
4. Whisk the eggs and sugar until the sugar has dissolved. Slowly pour the chocolate mixture over the egg mixture and beat until thoroughly combined.
5. Fold in the sieved flour and vanilla extract. Stir until all the flour has been incorporated. Pour into the prepared tin.
6. Bake for 45 minutes until the sponge is springy to the touch and has come away from the edge of the tin. Leave to cool in the tin for 5 minutes then remove and finishing cooling on a wire rack.
To make the cheesecake filling:
1. Place the gelatine leaves in a bowl and soften with a little water.
2. Heat the cream in a pan until it comes to the boil. Remove from the heat.
3. Squeeze the excess water from the gelatine leaves and add to the hot cream. Stir until the gelatine dissolves. Leave to cool.
4. Beat the cream cheese with the sugar until it’s soft.
5. In a separate bowl beat the egg whites until stiff.
6. Add the cooled gelatine to the cream cheese and beat well. Fold in the egg white. Carefully fold the crushed Oreo biscuits through the mixture.
1. Lightly grease a 23cm spring form tin.
2. Take the cooled chocolate sponge and cut in half to make 2 discs. Place on disc in the base of the tin. Pour the cheesecake mixture on top of the base. Gently sit the other sponge disc on top. Place in the fridge to set for at least 6 hours or overnight.
3. Carefully remove the cake from the tin and place on a serving plate or cake stand.
4. To decorate, spread the caramel caramel over the top and sprinkle with crushed Oreo biscuits.