Heat oven to 350ºF. Wrap foil around bottom and side of ungreased 9 inch springform pan. In a large bowl, mix crust ingredients with fork until crumbly. Press in bottom and up sides of springform pan. About 1 inch up sides. Bake 12 minutes and then cool 30 minutes.
In small microwaveable bowl, mirowave chocolate on High 45 to 50 seconds increments, stirring until melted. Set aside.
In a large bowl, beat cream cheese and sugar with electric mixer on medium speed, scraping bowl frequentlyl, until smooth and creamy. Add eggs one at a time, beating until smooth after each addition. Stir in Liqueur. Pour filling evenly over crust.
Drop 8 to 10 tablespoons melted chocolate randomly onto filling, allowing chocolate to sink into filling. With table knife or small spatula, cut through chocolate and filling to swirl for marbled design.
Bake 1 hour 10 minutes to 1 hour 20 minutes or until set 2 inches from edge of pan. Remove from oven; run knife around side of cheesecake to loosen. Return to oven; turn oven off and open door slightly. Cool cheesecake in oven 1 hour.
Remove from oven to cooling rack; cool at room temp. 1 hour. Refrigerate 3 hours or over night.
NOTE: I use Andes Crème de Menthe cookies crushed up for the crust.