1. Prepare CHOCOLATE CRUMB CRUST. Increase oven temperature to 450°F.
2. Beat cream cheese, 3/4 cup sugar, sour cream and 2 teaspoons vanilla in large bowl on medium speed of mixer until smooth. Gradually add flour, beating just until blended. Add eggs, one at a time, beating well after each addition.
3. Combine cocoa and remaining 1/4 cup sugar in medium bowl. Add oil, remaining 1/2 teaspoon vanilla and 1-1/2 cups of cream cheese mixture; stir well. Spoon plain and chocolate batters alternately over prepared crust, ending with spoonfuls of chocolate on top; gently swirl with knife for marbled effect.
4. Bake 10 minutes. Without opening oven door, reduce oven temperature to 250°F; continue baking 30 minutes. Turn off oven; without opening oven door, leave cheesecake in oven 30 minutes.
5. Remove from oven. Immediately loosen cheesecake from side of pan with knife; cool to room temperature. Refrigerate several hours or overnight; remove side of pan. Cover; refrigerate leftover cheesecake. Makes 12 servings.
CHOCOLATE CRUMB CRUST: Heat oven to 350°F. Combine 1-1/4 cups vanilla wafer crumbs (about 40 wafers, crushed), 1/3 cup powdered sugar and 1/3 cup HERSHEY'S Cocoa; stir in 1/4 cup (1/2 stick) melted butter or margarine. Press mixture onto bottom and 1/2 inch up side of 9-inch springform pan. Bake 8 minutes; cool completely.