(Blueberry Sauce)

1. Pop the blueberries, sugar, cornstarch, lemon zest, and lemon juice in a small saucepan. Bring the sauce to a boil, then lower the heat to a simmer and cook until the sauce has thickened (about 10 minutes). Once the sauce is nice and thick, remove the pan from heat and let it cool completely. Remove the lemon zest before adding the sauce to the cheesecake.

(Crust)

1. While the blueberry sauce is cooling, mix the graham cracker crumbs, butter, and sugar until well combined. Line a 9″ square pan with parchment paper and pack the graham cracker crumbs down in an even layer at the bottom of the dish. Freeze the crust for 30 minutes.

 (Cheesecake)

1. Pop the cream cheese and condensed milk in a large bowl and mix on medium speed until the cheese is smooth. Mix in the sour cream and the vanilla then spread the cheesecake mixture evenly over the prepared crust. 
2. Plop large spoonfuls of blueberry sauce on top of the cheesecake, then drag a knife or skewer through the cake making small figure eights. Gently lay a piece of plastic wrap directly over the top of the cheesecake (this prevents frostbite), then freeze the cake until firm (about 6 hours). 
3. Move the cake into the fridge 30 minutes before serving.