Preheat your oven to 160ºC (325ºF) and prepare a 23 cm (9-inch) springform pan by lining the bottom with parchment paper.

In a food processor, combine the digestive or graham crackers with the granulated sugar and melted butter until resembling wet sand. Press into the bottom of the pan and bake for 10 minutes.

In a mixing bowl, toss fresh blueberries with granulated sugar, flour, and lemon juice. Set aside. For the crumble, mix flour and brown sugar, then blend in melted butter until crumbly.

Beat cream cheese in a large bowl until smooth. Gradually add sugar, then stir in sour cream and cornstarch. Add eggs two at a time, mixing gently.

Pour cheesecake filling into the cooled crust, folding in blueberry mixture. Sprinkle crumble topping over the blueberries.

Place the springform pan into a larger baking pan filled with hot water and bake for 80-90 minutes or until center is slightly wobbly but set.

Once baked, turn off the oven and leave the door ajar for 1 hour to cool. Then, refrigerate for at least 6 hours or overnight.