Sweetened whipped cream and chocolate shavings (optional)
Directions
In 3-quart saucepan, with wire whisk, combine sugar and 1 1/2 cups milk; heat on medium-high until bubbles form around edge of pan. Remove from heat and add chocolate. Let stand 1 minute, then whisk until chocolate melts.
Meanwhile, in medium bowl, whisk cocoa, cornstarch, and remaining ½ cup milk until smooth. Whisk in eggs until blended. Whisking constantly, add 1/2 cup hot chocolate mixture in slow stream.
Heat chocolate mixture remaining in pan on medium-low. Whisking constantly, gradually add egg mixture to pan. Cook, whisking constantly, 10 minutes or until mixture becomes very thick and begins to bubble. Whisk in vanilla. Divide among 6 small serving cups.
Refrigerate until cold, 4 hours or up to 2 days. Top with whipped cream and shaved chocolate.