Crust: Mix ingredients. Press 1-1/3 cups of the crumb mixture firmly onto bottom of each of 4 (9-inch) springform pans. Bake at 325°F for 10 minutes. Cool on wire racks while preparing filling.
Filling: Beat cream cheese in large bowl of electric mixer fitted with paddle attachment on medium speed until creamy. Add sugar; beat until well blended. Add sour cream and vanilla; mix well. Add eggs, 1 at a time, mixing on low speed after each addition just until blended. Stir in melted chocolate.
Pour 1-1/2 qt. of the batter over each crust. Place each pan on large sheet of foil; wrap foil tightly around side of pan. Place springform pans on oven racks placed in full size hotel pans. Fill each hotel pan with 1 gallon hot water.
Bake at 325°F for 1 hour 10 minutes to 1 hour 20 minutes or until center is almost set. Run knife or metal spatula around side of each pan to loosen cake; cool before removing side of pan. Refrigerate 4 hours or overnight.