1. Place red bean, black glutinous rice, tangerine peel, and water in a pot and bring to a boil. Reduce heat and simmer for 2 to 3 hours, until the red bean is soft and the liquid is slightly reduced and thickened.
2. Add rock sugar and a pinch of salt into the pot and stir until all the sugar has melted.
3. Turn off heat. Serve hot or warm with a side of coconut milk.