1. Prepare CHOCOLATE CRUMB CRUST.
2. Increase oven temperature to 450°F. Combine cream cheese, sugar, sour cream, cocoa and vanilla in large bowl; beat on medium speed of mixer until smooth. Add flour and eggs; beat well. Pour into prepared crust. Bake 10 minutes.
3. Reduce oven temperature to 250°F; continue baking 30 minutes. (Cheesecake may not be set in center.) Turn off oven; leave cheesecake in oven 30 minutes without opening oven door. Remove from oven to wire rack. With knife, loosen cake from side of pan. Cool to room temperature; remove side of pan. Refrigerate several hours before serving. Garnish with chocolate curls or sliced fruit and whipped cream, if desired. Cover; refrigerate leftover cheesecake. 10 to 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 in medium bowl; 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 to 10 minutes. Cool.