Preheat your oven to 160ºC (325ºF). In a food processor, combine 250 g of digestive or graham crackers with 2 tablespoons of granulated sugar, blending until fine crumbs form. Melt 75 g of butter, then mix it into the crumbs until fully coated. Press this mixture firmly into the base of a lined 9-inch springform pan. Bake for 10 minutes, then let it cool completely before adding the filling.

In a medium bowl, gently mix 300 g of fresh blueberries with 260 g of granulated sugar, 1 tablespoon of all-purpose flour, and 2 teaspoons of lemon juice. Set this delightful blueberry mixture aside. For the crumble, in another bowl, combine 110 g of all-purpose flour with 80 g of dark brown sugar. Pour in melted 70 g of butter, mixing till the mixture resembles coarse crumbs. Set this crumble aside to allow the flavors to meld.

In a large mixing bowl, beat 800 g of full-fat cream cheese using an electric mixer until creamy and smooth. Gradually add 260 g of granulated sugar, ensuring it combines well. Stir in 200 g of sour cream and 1½ tablespoons of cornstarch until fully integrated. Add 4 large eggs two at a time, blending gently until everything is just combined. This creamy mixture is the heart of your Blueberry Crumble Cheesecake.

Pour the silky cheesecake filling over the cooled crust, smoothing it out with a spatula. Scatter your prepared blueberry mixture evenly over the filling, followed by the crumble topping. Ensure an even distribution to create beautiful layers that will blend perfectly during baking. This step will lay the foundation for the lusciousness of the cheesecake.

For the perfect bake, place the springform pan in a larger baking dish filled with hot water, creating a water bath. This helps prevent cracking. Bake in the preheated oven for 1 hour 20 to 30 minutes. The cheesecake should be slightly jiggly in the center when done. Once baked, turn off the oven and let the cheesecake cool in the warmth for an hour before transferring it to the refrigerator for at least 6 hours or overnight.