1. In a small saucepan, combine the blueberries, sugar, cornflour, and water. Stir until the cornflour dissolves completely.
2. Cook the mixture over medium heat, stirring frequently, until it comes to a boil. Reduce the heat to low and let the mixture simmer for 5-10 minutes, or until it thickens to your desired consistency.
3. Remove the saucepan from the heat and let the mixture cool completely.
4. Crush the digestive biscuits into fine crumbs. In a mixing bowl, combine the biscuit crumbs and melted butter. Mix well until the mixture is well combined and press into the base of an 8 inch springform cake tin. Place in the fridge to chill for 30 minutes.
5. In a mixing bowl, beat the cream cheese until smooth. Add the heavy cream, sugar, and vanilla extract. Beat until well combined.
6. In a separate small bowl, soak the gelatine sheets in cold water for 5-10 minutes, or until they become soft.
7. Squeeze the excess water from the softened gelatine sheets and add them to the hot water. Stir until the gelatine is completely dissolved.
8. Add the dissolved gelatine to the cream cheese mixture and mix well.
9. Pour half the cheesecake mixture over the chilled biscuit base, then pour in half the blueberry mix and then the remaining creamy cheesecake filling. Cover with cling film. Chill the cheesecake in the fridge for at least 4 hours, or until it's set.
10. Once the cheesecake has set, remove it from the tin and transfer to a cake stand. Put parchment paper under the cheesecake if doing the outer chocolate layer.
11. To create the outer chocolate layer, fold a long strip of parchment in half and half away lengthways. This offers stability. Melt the white chocolate and pour it along the length of the parchment. Using a cranked palette knife spread it out evenly. Allow to sit for 5 minutes. Then swiftly lift it up and carefully place it around the cheesecake. Put it in the fridge to set for 30 minutes. Repeat and do the same again if doing a second layer. Each layer uses about 300g of chocolate.
