PREHEAT oven to 325°F if using a silver 9-inch springform pan (or to 300°F if using a dark nonstick 9-inch springform pan). Mix crushed cookies and butter; press firmly onto bottom of pan.
BEAT cream cheese, sugar and vanilla with electric mixer on medium speed until well blended. Add melted chocolate; mix well. Add eggs, 1 at a time, mixing on low speed after each addition just until blended. Pour over crust.
BAKE 55 minutes to 1 hour or until center is almost set. Run knife or metal spatula around side of pan to loosen cake; cool before removing side of pan. Refrigerate 4 hours or overnight. Store leftover cheesecake in refrigerator.