1) Combine the sugar, cocoa, salt, espresso powder, chocolate chips, and water in a saucepan set over medium heat.
2) Bring the mixture to a boil and cook, stirring frequently, until the chips and sugar are dissolved.
3) Remove from the heat, and stir in the vanilla and Kahlua or vodka. Transfer the mixture to a heatproof bowl, and refrigerate until thoroughly chilled; overnight is best.
4) Freeze the mixture in your ice cream maker, according to the manufacturer's instructions. It'll remain quite soft; freeze for several hours before serving, to firm up.
Yield: about 3 cups sorbet.