Toast the nibs. Toast the cacao nibs in a dry skillet over medium-low heat for 5 to 8 minutes, stirring often, until they smell like chocolate. Let them cool slightly.
Grind. Grind the nibs in a mortar and pestle in small batches until they form a coarse, oily paste. This takes patience, and the paste will stay slightly gritty.
Rehydrate the chiles. Cover the chiles with hot water and soak for 15 minutes until soft.
Boil the peppers. Drain the chiles, then simmer them in the 2 cups of water for 8 to 10 minutes. Remove the chiles, or blend a small piece back in for more heat.
Add the cacao. Whisk the cacao paste into the chile water and simmer gently for 5 to 8 minutes, whisking often.
Finish. Remove from the heat. Stir in the vanilla and honey, and taste. Add a pinch of salt if you like.
Froth and serve. Pour the drink back and forth between two cups from a height to build foam, then serve.