Preheat your oven to 325°F (160°C).

In a mixing bowl, combine graham cracker crumbs, granulated sugar, and melted butter until the texture resembles wet sand. Firmly press this mixture into the base of small jars or lined cupcake cups. Bake for 5 to 7 minutes, then set aside to cool completely.

In a large bowl, beat the softened cream cheese until smooth. Add in granulated sugar and mix until fully incorporated. Gradually add in eggs, mixing gently after each addition. Stir in sour cream, fresh lemon juice, lemon zest, and vanilla extract until smooth.

Pour the cheesecake filling over the cooled crusts, filling each cup about three-quarters full. Gently tap on your counter to release air bubbles.

Place the filled cups in the oven and bake for 18 to 22 minutes, or until the centers are slightly jiggly. Allow them to cool at room temperature before refrigerating for at least 3 hours or until fully set.

In a saucepan over medium heat, combine blueberries, sugar, and lemon juice. Cook until the berries start releasing their juices. Stir in the cornstarch slurry and cook until the mixture thickens, then remove from heat and allow to cool.

Once the cheesecake cups are chilled and the blueberry sauce is cooled, spoon the sauce over each cup. Garnish with fresh blueberries and lemon zest if desired.