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 cookie crumbs and butter; press firmly onto bottom of pan.
BEAT cream cheese, sugar and vanilla in large bowl 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 minute to 1 hour 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 4 hours or overnight. Store leftover cheesecake in refrigerator.
Dust entire surface of cooled cheesecake with cocoa powder using a wire mesh strainer. For a festive Valentine's Day garnish, create a heart-shaped design by topping dusted cheesecake with a heart-shaped stencil and sprinkling with powdered sugar.