Preheat your oven to 325°F (160°C). In a mixing bowl, combine graham cracker crumbs, granulated sugar, and melted unsalted butter until well blended. The mixture should resemble wet sand. Press this firmly into the bottom of a springform pan to create a compact crust. Bake for 8-10 minutes, just until set and lightly golden, then let it cool while preparing the filling.

In a large bowl, beat the cream cheese with an electric mixer on medium speed until it's smooth and creamy, about 1-2 minutes. Gradually add granulated sugar, mixing until combined. Add eggs one at a time, ensuring each is fully incorporated. Blend in sour cream, heavy cream, fresh lemon juice, lemon zest, and vanilla extract until the mixture is smooth and silky. Gently fold in fresh blueberries and sprinkle in the flour, ensuring the batter remains airy.

Pour the filling over the cooled crust evenly and smooth the top with a spatula. Bake in the preheated oven for 100 minutes, or until the edges are set but the center still has a slight jiggle. After baking, turn off the oven, and leave the cheesecake inside with the door slightly ajar for 1 hour, which helps prevent cracking.

While the cheesecake cools, prepare your blueberry topping. In a saucepan over medium heat, combine fresh blueberries, granulated sugar, and water. Cook until bubbling, about 5 minutes. In a small bowl, mix cornstarch with a tablespoon of cold water to create a slurry, then stir it into the pan. Cook for an additional 2-3 minutes, stirring until thickened, then remove from heat and stir in fresh lemon juice and vanilla extract.

Once the cheesecake has cooled to room temperature, refrigerate it for at least 5 hours, or overnight for the best results. This chilling time allows the flavors to meld beautifully. Before serving, top the cheesecake with the luscious blueberry mixture, spreading it evenly for a delightful presentation.