Preheat oven to 150°C fan forced. Invert base of a 22cm (base) springform cake pan. Grease and line base with baking paper.
Process biscuits in a food processor until finely crushed. Add butter. Process until combined. Press over the base and three-quarters of the way up the side of the prepared pan. Refrigerate for 15 minutes.
For the filling; Using an electric mixer, beat cream cheese, sugar and caramel spread until smooth. Add egg yolks and corn flour, mix well. Fold in sour cream, then the blueberries. Spoon into prepared pan and smooth the top. Place onto a flat tray, bake for about 45-50 minutes, or until just set. Turn off the oven. Cool in the oven with door ajar for 1 hour. Remove. Refrigerate for 6 hours, or overnight until firm.
Combine chocolate and cream in a heatproof bowl. Sit over a saucepan of simmering water. Stir until melted and smooth. Cool slightly. Spread the chocolate mixture evenly over the top of the cheesecake. Refrigerate until set. Decorate with extra blueberries, just before serving.