Combine in a small heatproof bowl:
- 1 ounce dark, bittersweet, or semisweet chocolate (60 to 72% cacao), chopped
- ¼ cup sugar
- ⅛ teaspoon salt
Combine in a saucepan:
- 1 ½ cups strong coffee
- 1 cup water
- 1 cup half-and-half
Bring to a boil, then pour over the chocolate, whisking to dissolve the chocolate and sugar completely. Stir in:
- 1 teaspoon vanilla
- Pinch of ground cinnamon