Preheat your oven to 325°F (160°C).

In a mixing bowl, combine graham cracker crumbs, melted butter, and granulated sugar. Mix until well blended.

Press the mixture firmly into the bottom of the springform pan to form the crust. Bake in the preheated oven for 10 minutes, then set aside to cool.

In another mixing bowl, beat the softened cream cheese with an electric mixer until smooth and creamy. Gradually add in the granulated sugar and continue to mix until well combined.

Add the eggs one at a time, mixing on low speed until just incorporated. Stir in the vanilla extract and sour cream, mixing until the mixture is smooth and creamy.

Pour the cheesecake filling over the crust in the springform pan. Smooth the top with a rubber spatula.

Bake in the oven for 50-60 minutes, or until the edges are set but the center is still slightly jiggly. Turn off the oven and let the cheesecake cool in the oven with the door slightly ajar for another hour.

While the cheesecake is cooling, prepare the blackberry sauce. In a saucepan, combine the blackberries, granulated sugar, lemon juice, cornstarch, and water. Cook over medium heat until the blackberries have softened and the sauce has thickened, about 10-15 minutes.

Once the cheesecake is completely cooled, drizzle the blackberry sauce over the top. Refrigerate the cheesecake for at least 4 hours, preferably overnight, to set before serving.

Before serving, garnish with fresh blackberries if desired. Slice and enjoy!