Prepare Blueberry Sauce: In a saucepan over medium heat, combine blueberries, granulated sugar, and lemon juice. Cook for about 5–7 minutes, stirring gently until the blueberries have softened and released their juices. Once bubbling, whisk in cornstarch to thicken the sauce, stirring for an additional 2 minutes until it coats the back of a spoon. Strain the sauce through a fine mesh sieve to remove skins and let it cool completely.

Preheat Oven: Preheat your oven to 325°F (160°C). Line a muffin pan with cupcake liners.

Make Crust: In a mixing bowl, combine graham cracker crumbs with melted unsalted butter and a touch of sugar until it resembles wet sand. Press this mixture firmly into the bottom of each cupcake liner in the muffin pan. Bake for about 5 minutes until lightly golden, then cool.

Prepare Filling: Beat cream cheese and granulated sugar in a bowl with an electric mixer on medium speed until creamy, about 2–3 minutes. Add lemon juice, lemon zest, and vanilla, mixing well.

Add Eggs: Add eggs to the cream cheese mixture one at a time, mixing gently on low speed after each addition until just combined.

Assemble Cheesecakes: Pour filling into muffin cups over the crusts, filling about three-quarters full. Spoon blueberry sauce on top and swirl gently for a marbled effect.

Bake: Bake for 17-20 minutes until the tops are set with a slight jiggle in the center. Cool for 1 hour.

Cool and Chill: Transfer the pan to the refrigerator and chill for at least 3-4 hours, or preferably overnight.