1. Place a heatproof glass or metal bowl over a pan of simmering water. Do not allow the bowl to touch the surface of the water.
2. Scrape the seeds from the vanilla bean (save the pod for another use).
3. Place the sugar, vanilla bean seeds, and wine in the bowl. Whisk the mixture until the sugar has completely dissolved.
4. Add the egg yolks and whisk constantly until the mixture has tripled in volume and a thermometer reads 140°F.
5. Remove the bowl from the heat and add 2 ounces finely chopped bittersweet chocolate.
6. Allow the sabayon to sit for a few moments without whisking, just until the chocolate melts. Then, continue whisking until the mixture is completely cooled.
7. Transfer the sabayon to a container with a tight-fitting lid and refrigerate until ready to use.

This wonderful recipe is adapted from Laura Frankel's Jewish Cooking for All Seasons. Serve a spoonful of the sabayon with Espresso Granita.