Positon rack in center of oven. Preheat to 300F. Grease a 10 inch springform pan. For crust, mix crumbs, cocoa, and sugar. Mix in butter. Spread onto bottom of pan.
For filling, melt chocolate. In large bowl, beat cream cheese and sugar. Beat in eggs one at a time. Stir in sour cream, chocolate, amaretto, and extracts. Pour mixture over crust. Bake about 1 hour or until firm. Turn off oven and leave cake in for about 30 minutes. Remove and let cool completely. Unmold onto plate.
For topping, melt chocolate and butter the same as above. Pour over top of finished cake.
I have found that the amaretto can be replaced with another liquer of your choosing, but remember to omit the almond extract. You can also try leaving out the liquer all together.