For the crust: pulse the graham crackers in a food processor until you get fine crumbs, melt the butter in the microwave or in a small saucepan, then pour it over the crumbs and mix until evenly moistened.
Once the crumbs have absorbed the butter, transfer the mixture to a 9‑inch (22 cm) round springform pan and press it firmly over the bottom and slightly up the sides using the bottom of a glass. Chill the crust in the refrigerator while you prepare the filling.
For the filling: in a large mixing bowl, combine the cream cheese and powdered sugar, then mix until smooth and creamy with no lumps.
Add the heavy whipping cream, eggs, and sour cream to the bowl, then mix just until everything is well combined.
Next, add the lemon juice and cornstarch, stirring again until the mixture is smooth and silky.
Take the pan with the crust out of the fridge and pour the cheesecake filling over it. Bake in a preheated oven at 230°F (110°C) for 1 to 1 ½ hours, until the edges are set and the center still has a slight wobble.
Place a baking dish filled with water on the lower rack of the oven to create steam while the cheesecake bakes, which helps keep the texture creamy and prevents cracks.
When the cheesecake is baked, let it cool at room temperature for about 2 hours, then refrigerate it for 5–6 hours, or until thoroughly chilled and set. Decorate the top generously with fresh blueberries before serving.