Pour water to depth of 1 inch into bottom of a double boiler over medium heat; bring to a boil. Reduce heat to low, and simmer. Whisk together first 6 ingredients in top of double boiler; whisk in chocolate. Cook, whisking constantly, 15 minutes or until mixture reaches 160°. (Mixture will continue to thicken as it cools.) Remove from heat, and cool 10 minutes. Spoon into demitasse, espresso, or tea cups. Cover and chill 12 hours. Serve with desired toppings.