1Heat oven to 350°F. Grease 9-inch glass pie plate. In small bowl, mix coffee and liqueur until coffee is dissolved.
2In large bowl, beat coffee mixture and remaining cheesecake ingredients with electric mixer on high speed 2 minutes, scraping bowl frequently. Pour into pie plate.
3Bake about 35 minutes or until center is firm and puffed. Cool 5 minutes (cheesecake top will be cracked).
4In small bowl, mix 1 ounce chocolate, the powdered sugar and 1 tablespoon liqueur until well blended. Stir in sour cream and 1 teaspoon vanilla. Carefully spread topping over cheesecake. Refrigerate at least 3 hours before serving. Store in refrigerator.