MIX crumbs and butter; press onto bottom of 9-inch springform pan. Bake at 325°F for 10 minutes if using a silver springform pan. (Bake at 300°F for 10 minutes if using a dark nonstick springform pan.)
BEAT cream cheese, sugar, flour and vanilla with electric mixer on medium speed until well blended. Blend in melted chocolate and liqueur. Add eggs, 1 at a time, mixing on low speed after each addition just until blended. Pour over crust.
BAKE at 325°F for 55 to 60 minutes or until center is almost set if using a silver springform pan. (Bake at 300°F for 60 to 65 minutes or until center is almost set if using a dark nonstick springform pan.) Run knife or metal spatula around rim of pan to loosen cake; cool before removing rim of pan. Refrigerate 4 hours or overnight. Garnish with sifted powdered sugar and mixed berries, if desired.
How To Press Crumb Mixture Into Pan To Make Crust:
Use bottom of straight-sided glass to evenly press cookie crumb mixture onto bottom of springform pan.