In a saucepan, combine half-and-half, chocolate, and sugar and place over medium-low heat, stirring frequently, until the chocolate melts.
Beat the egg yolks in a small bowl, then whisk in about 1/2 cup of the chocolate mixture. Whisk the egg mixture into the soup and simmer, stir frequently, until the soup thickens slightly, about 5 minutes. Remove from heat and stir in the liqueurs.
To serve hot, ladle into warmed bowls, add a dollop of whipped cream, sprinkle with the hazelnuts, and serve immediately. Alternatively, pour a container, tightly cover, and refrigerate for up to 5 days. Slowly reheat before garnishing and serving.
To serve cold, pour into a container, tightly cover, and refrigerate until chilled, at least 2 hours or as long as 5 days. Remove from the refrigerate about 20 minutes before serving. Ladle into chilled bowls and garnish as for hot soup.
Serves 6 as a brunch soup course or dessert.
[mc-recipe-=patH 01 Oct 96]