Preheat your oven to 160ºC (325ºF) and line the bottom of a 9-inch springform pan with parchment paper.

In a food processor, blend digestive or graham crackers with granulated sugar until finely crushed. Mix in melted butter. Press this mixture into the bottom of your prepared pan. Bake for 10 minutes or until golden, then let it cool.

In a mixing bowl, combine fresh blueberries, granulated sugar, all-purpose flour, and lemon juice. Set aside.

Whisk all-purpose flour and dark brown sugar in a bowl. Add melted butter and mix until crumbly. Set aside.

Beat cream cheese and granulated sugar in a large mixing bowl until smooth. Add sour cream, cornstarch, and vanilla extract, mixing well. Gradually add eggs, two at a time, beating gently.

Pour the cheesecake batter into the cooled crust. Sprinkle the blueberry mixture over it, then add the crumble topping. Bake in a water bath for 1 hour and 20-30 minutes until the center is gently jiggly.

Turn off the oven and leave the cheesecake inside for about 1 hour. Let it cool to room temperature on a wire rack, then refrigerate for at least 6 hours or overnight.