Beat the mascarpone with the cheese, caster sugar, cornflour, lime zest and eggs. Spoon half of the cheese mix into the tin, add most of the blueberries (keeping some for the top) and pour over the remaining mixture. Smooth the top. Bake for 40 minutes or until the mixture is set but with a faint wobble in the centre, spoon over the soured cream and bake for a further 10 minutes. Leave to cool completely. Release the cheesecake from the tin and spoon the remaining fruit and the reserved juices on top or serve them with the cheesecake slices.