Process digestive biscuits in your food processor to a powdery consistency. Add butter and vanilla extract and distribute evenly in a 25cm springform tin, shaping a 2cm edge all around. Gently press to firm it up.
For the filling beat eggs with cream cheese using your electric mixer. Add vanilla extract and sugar and beat till well combined.
Tip filling into the tin. Bake in the preheated oven till the filling is set, 45 to 50 minutes. Remove from the oven, let cool slightly, then remove rim.
In a small saucepan combine blueberries and sugar. Bring to the boil. Stir cornflour with 1 to 2 tablespoons cold water to dissolve, then quickly stir into the blueberry mix and continue stirring till the mixture thickens and turns clear again.
Spread on the cake while still warm. Let set, then refrigerate till well chilled.