1. Preparing the Crust

1. Preheat the oven to 325°F (163°C).
2. In a mixing bowl, combine chocolate graham cracker crumbs, sugar, and melted butter.
3. Press the mixture into the bottom of a 9-inch springform pan.
4. Bake for 10 minutes, then remove from the oven and allow to cool completely.

2. Making the Cheesecake Batter

1. In a large bowl, beat the cream cheese with an electric mixer until smooth and lump-free.
2. Add sugar and sour cream, mixing until well combined.
3. Mix in vanilla extract.
4. Add eggs one at a time, beating on low speed after each addition until smooth.

3. Creating the Blueberry Swirl

1. In a small saucepan, combine blueberries, sugar, and lemon juice.
2. Cook over medium heat until the blueberries release their juices and soften.
3. Stir in cornstarch mixed with water and cook for 1-2 minutes until the mixture thickens.
4. Allow to cool before using.

4. Assembling and Baking

1. Pour the cheesecake batter over the cooled crust in the springform pan.
2. Drop spoonfuls of the blueberry mixture on top of the batter and swirl with a knife or skewer to create the swirl pattern.
3. Bake for 55–60 minutes, until the center is set but still slightly jiggly.
4. Turn off the oven and let the cheesecake cool in the oven for 1 hour with the door cracked.
5. Refrigerate for at least 4 hours or overnight to set fully.