Preheat the oven to 325°F. Place an 8 x 8 pan on the bottom rack and fill halfway with boiling water.
Spray a 9 inch springform pan with cooking spray. Wrap the outside of the bottom of the pan with heavy duty aluminum foil, to prevent any leakage. Set aside.
In a medium-size mixing bowl toss together graham crumbs with granulated sugar and butter until fully moistened. Press evenly onto the bottom and halfway up the sides of the pan. Place the pan into the freezer while you make the filling.
Using an electric mixer, whip together cream cheese, sugar and vanilla until completely smooth. Add cornstarch and vanilla, mixing well.
Add eggs one at a time, mixing well after each addition. Scrape sides and bottom of bowl as needed. Mix in sour cream by hand.
Pour evenly into the crust. Bake on the middle rack of the oven for 1 hr 10 - 1 hr 20 minutes or until the center is still slightly loose when gently shaken. It won't be completely set. Turn off the oven, leave the door slightly ajar, and leave cheesecake in the oven for 1 hour longer to finish baking.
Remove to a cooling rack, and allow to cool for 30 minutes then run a knife gently around the top edge. Cool completely to room temperature. Leave the ring in place, wrap and chill for 1 preferably 24 hours.
Slice and serve with fresh fruit and whipped cream or any of your favorite toppings.