PREHEAT oven to 300°F if using silver 9-inch springform pan (or to 275°F if using dark nonstick 9-inch springform pan). Mix cookie crumbs and butter; press firmly onto bottom of pan. Set aside.
BEAT cream cheese, sweetened condensed milk and vanilla in large bowl with electric mixer on medium speed until well blended. Add chocolate; mix well. Add eggs, one at a time, mixing on low speed after each addition just until blended. Pour over crust.
BAKE 1 hour 5 min. to 1 hour 10 min. or until center is almost set. Run knife or metal spatula around rim of pan to loosen cake; cool before removing rim of pan. Refrigerate at least 4 hours or overnight. Store leftover cheesecake in refrigerator.