Crust: Mix together cookie crumbs, sugar and butter; press into the bottom of a 9" springform pan.
Bake@ 325 degrees for 10 minutes.
Filling: Mix together cream cheese, sugar and vanilla with an electric mixer until well blended.
Add chocolate, liqueur and eggs; mix just until blended.
Pour over crust.
Bake at 325 for 55-60 minutes or until center is almost set if using a silver springform pan (bake at 300 degrees for 60-65 minutes or until center is almost set if using a dark nonstick springform pan).
Run knife or metal spatula around the rim of pan to loosen cake; cool before removing the rim of pan.