Kelp and pork bone soup

Put the pork bones and a knob of ginger in 2.5 liters of cool water; bring to a boil.

As it comes to a simmer, skim; add some cool water, return to a boil and skim again, three times in all.

Keep at a heavy simmer, almost a light boil, covered with the lid ajar, for two hours.

Soak 20 g dried kelp in cool water at least half an hour and up to two hours.

Rinse the kelp thoroughly of sand and squeeze out excess water; roll each piece tightly like a log and slice into about half-centimetre slivers.

When the soup is milky, add the kelp, stir and cook another 30 minutes.

Season each bowl to taste with salt, sugar, optional MSG and white pepper, and sprinkle with sliced scallions.