Tye the pork loin with twine so that it can be stuffed and roasted evenly.
Strike the ginger root with the spine of a kitchen knife, then chop the long onion.
Put (1), (2) and (A) into a deep pot, then heat with the star anise and enough water to cover the pork loin.
Add water if too much evaporates while cooking, and cook until the pork becomes soft.
Allow to cool as is.
Cut (3) into easy-to-eat pieces.
Serve with water from (3) poured on and garnished with mustard paste.
* Accompany with cherry tomatoes and other vegetables if you like.