PREHEAT oven to 350º F. Grease 9-inch springform pan.
COMBINE graham cracker crumbs, butter and granulated sugar in medium bowl. Press onto bottom of prepared pan. Sprinkle with 1/2 cup morsels.
MICROWAVE remaining morsels in medium, uncovered, microwave-safe bowl on HIGH (100%) power for 30 seconds; STIR. The morsels may retain some of their original shape. If necessary, microwave at additional 10- to 15-second intervals, stirring just until morsels are melted; cool to room temperature.
BEAT cream cheese, granulated sugar and brown sugar until smooth; beat in pumpkin. Beat in eggs, evaporated milk, cornstarch, cinnamon and nutmeg. Remove 3/4 cup pumpkin mixture; stir into melted chocolate. Pour remaining pumpkin mixture into crust. Spoon chocolate-pumpkin mixture over top; swirl.
BAKE for 60 to 65 minutes or until edge is set but center still moves slightly. Cool in pan on wire rack. Refrigerate for several hours or overnight. Remove side of springform pan.