Prepare the crust:
Preheat the oven to 325°F (163°C). In a medium bowl, combine the graham cracker crumbs, sugar, and melted butter. Mix well until the crumbs are evenly coated. Press the mixture into the bottom of a 9-inch springform pan to form a firm crust. Bake for 8-10 minutes and then let it cool.

Make the filling:
In a large bowl, beat the softened cream cheese until smooth and creamy. Add the sugar and continue to beat until fully combined. Add the eggs one at a time, beating well after each addition. Stir in the vanilla extract, sour cream, and heavy cream. Mix until smooth.

Bake the cheesecake:
Pour the cream cheese filling into the cooled crust. Smooth the top with a spatula. Bake for 50-60 minutes, or until the center is set and the edges are lightly browned. Turn off the oven and let the cheesecake cool in the oven with the door slightly open for about 1 hour. Then refrigerate for at least 4 hours or overnight.

Make the blueberry topping:
In a saucepan, combine the blueberries, sugar, lemon juice, and water. Cook over medium heat, stirring occasionally, until the blueberries begin to release their juice (about 5-7 minutes). If you prefer a thicker topping, whisk the cornstarch into a small amount of water and add it to the blueberry mixture. Cook for another 1-2 minutes until it thickens. Let the blueberry mixture cool before pouring it over the cheesecake.

Assemble the cheesecake:
Once the cheesecake has chilled, spread the cooled blueberry topping evenly over the top. Slice and serve chilled.