Butter all sides of an 8" springform pan. Wrap aluminum foil all around the outside sides and under the outside bottom of the pan.
Combine the first four (4) ingredients thoroughly. Press evenly and firmly onto the bottom of the buttered pan.
Preheat the oven to 350 F degrees.
Beat cream cheese until smooth.
Gradually add the sugar, mixing until well blended.
Add eggs one at a time and beat at low speed with a hand-held mixer until smooth.
Melt the chocolate with whipping cream, stirring frequently until smooth.
Add chocolate mixture to the cream cheese mixture, blending well.
Mix in sour cream, followed by the cooled espresso, then the liqueur and vanilla. Beat until well blended.
Pour into the springform pan and bake for 60 minutes or until sides are slightly puffed (the center will still be a bit soft, but will firm up when chilled).
Cool cake in the pan on a wire rack.
Refrigerate for at least 12 hours before serving.
Remove the sides of the springform pan and garnish.