6 oz. unsweetened chocolate, broken into 1/2-oz. pieces
2 oz. semisweet chocolate, broken into 1/2-oz. pieces
1 tsp. pure vanilla extract
Heat water, sugar and coffee in saucepan over medium-high heat. Whisk to dissolve sugar. Bring mixture to a boil. Place chocolates in stainless steel bowl.
Remove boiling liquid from heat, and pour 1 cup over chocolate. Allow to stand for 5 minutes. Whisk until completely smooth, about 3 minutes. Add remaining hot liquid, and whisk until smooth. Cool in ice-water bath to temperature of 40 to 45F. When cold, stir in vanilla.
Freeze in ice cream freezer. Transfer semifrozen sorbet to plastic container,securely cover and place in freezer for several hours. Serve within two days.