The sauce can be made while the cake is cooking or many days in advance.
In a large saucepan over medium heat, combine blueberries, water and sugar. Stir frequently, but careful not to crush the berries, bring to a low boil.
In a small bowl, mix the cornstarch with cold water until combined.
Slowly stir the cornstarch into the blueberries, careful not to crush them. Simmer until the homemade blueberry sauce is thick enough to coat the back of a metal spoon, about 10 minutes.
Remove from heat and gently stir in vanilla.
Let the sauce cool at room temperature. Measure 1/2 cup for your recipe; store the rest in jars in the fridge.
Preparing the Crust:
In a large bowl, mix the crumbs with melted butter and granulated sugar with a rubber spatula until combined.
Press the mixture into the bottom of a 9inch spring form cake pan and slightly up the sides. Make sure it is tight and compact.
Chill the crust for 15 minutes.
Preheat oven to 325F.
In the bowl of an electric mixer fitted with the wire attachment beat cream cheese on medium speed until fluffy. Add the sugar, cornstarch, lemon juice, lemon zest and beat until combined.
Add eggs, one at a time, beating until just combined after each addition. On low speed beat in sour cream just until combined.
Remove crust from the fridge and pour the batter into the crust.
In circles pour the blueberry sauce over the cheesecake and with the edge of a spatula create swirls and mix the blueberry sauce into the cheesecake filling. Carefully not to over mix.
Bake for about 1 1/4 hours or until center is almost set. Cool on a wire rack for 15 minutes. Sprinkle graham crackers on top and loosen sides of pan and continue cooling on wire rack until the cheesecake is at room temperature.
Transfer to the fridge. Refrigerate overnight or at least 6 hours before serving.
The cheesecake can be served with warm blueberry sauce.