Bring the water to the boil in a shallow pan that the pork will fit into quite snugly, but with a few gaps to spare. Put in the pork and when it comes back to the boil, remove any scum.
Add the sherry or sake and simmer for 30 minutes. Add the spices, ginger, chilli flakes, soy, red currant jelly, and balsamic vinegar. Bring back to the boil and simmer, covered, on a very low heat or in a very low oven for 2–3 hours, carefully turning the meat from time to time.
Add the garlic after 1 hour of cooking.
When a thin skewer inserted into the meat offers absolutely no resistance, then the meat is cooked.
Gently remove onto a serving dish along with the pieces of ginger and garlic, and keep warm.
Reduce the sauce until of a syrupy consistency but watch out for excess saltiness due to the soy sauce, so keep tasting.
Spoon the sauce over the meat and strew with the spring onions, cilantro sprigs, and chilli. The meat can be eaten with a spoon, the bones will just slip out and the fat and rind will be lusciously soft and melting.