PREHEAT oven to 350°F. Mix baking crumbs and butter; press firmly onto bottom of 9-inch springform pan. Beat cream cheese and sugar in large bowl with electric mixer on medium speed until well blended. Add pumpkin, pumpkin pie spice and cornstarch; mix well. Add eggs, 1 at a time, mixing on low speed after each addition just until blended. Pour over crust.

BAKE 50 to 55 minutes or until centre is almost set; cool slightly. Spread with sour cream. Loosen cake from rim of pan; cool before removing rim of pan.

PLACE chocolate and oil in small microwaveable bowl. Microwave on MEDIUM 1 minute; stir until chocolate is completely melted. Drizzle over cheesecake in spiral pattern. Starting at centre of cheesecake, pull a toothpick through the lines to outside edge of cheesecake to resemble a spider's web. Refrigerate at least 4 hours or overnight. Store leftover cheesecake in refrigerator.