Grind the chocolate wafers and 3 ounces of chocolate in a food processor; the crumbs should be small. Mix in 3 tablespoons of sugar. Melt 7 tablespoons of butter or margarine, and add it to the chocolate crumbs. Press into the bottom of a 9 inch springform pan.
Melt 12 ounces of chocolate, and cool slightly. Blend in cream cheese, 1 3/4 cups sugar, eggs, 1/2 cup cream, cocoa, vanilla, and peppermint extract. Pour this in crust. Bake for one hour at 350 degrees F (175 degrees C). Cool overnight.
In a small bowl, mix together the sour cream and 1/4 cup sugar. Pour on top of cooled cheesecake. Bake for 20 minutes at 350 degrees F ( 175 degrees C). Chill for 6 to 8 hours.
To decorate the cheesecake make a chocolate icing. In a small saucepan, simmer 1/2 cup cream and 1 tablespoon butter. Add to this 6 ounces of chocolate, and stir until melted. Remove from heat. Freeze until the mixture is piping consistency (stir occasionally). Using a pastry bag, pipe a lattice on the top.
