Preheat your oven to 160ºC (325ºF). In a food processor, blend digestive or graham crackers with 2 tablespoons of granulated sugar until finely crushed. Add 75 g of melted butter, mixing until combined. Press this crumb mixture firmly into the bottom of a springform pan, ensuring an even layer. Bake for 10 minutes until lightly golden, then remove and let it cool completely.

In a medium bowl, combine 300 g of fresh blueberries with 60 g of granulated sugar, 1 tablespoon of all-purpose flour, and 2 teaspoons of lemon juice. Gently toss to coat and set aside. In another bowl, mix 110 g of all-purpose flour and 80 g of brown sugar, then stir in 70 g of melted butter until crumbly.

In a large mixing bowl, beat 800 g of full-fat cream cheese on low speed until smooth and creamy. Gradually add 260 g of granulated sugar, mixing until fully incorporated. In a separate bowl, stir together 200 g of sour cream with 1 ½ tablespoons of cornstarch, then fold this mixture into the cream cheese. Add 4 large eggs one at a time, mixing thoroughly after each addition.

Pour the cheesecake filling over the cooled crust in the springform pan. Carefully spread the blueberry mixture evenly on top, then sprinkle the crumble topping generously over the blueberries. Place the springform pan in a larger baking dish and fill it with hot water to create a water bath. Bake for 1 hour and 20-30 minutes until the cheesecake is set but slightly wobbly in the center.

Turn off the oven and leave the cheesecake inside with the door ajar for 1 hour. After an hour, remove the cheesecake from the oven and let it come to room temperature. Once cooled, refrigerate for at least 6 hours, preferably overnight, to fully set and develop flavors.