Kkori Gomtang

Method

1. Put 250 g of oxtail in a bowl, cover generously with cold water and leave to soak for 3 hours, changing the water two or three times. The water should run pale pink rather than red at the end; this is what keeps the finished broth clean-tasting and ivory rather than grey.
2. Drain the oxtail, put it in a heavy pot, cover with fresh cold water and bring to a hard boil over high heat. Boil for 10 minutes, letting the brown scum rise. Tip everything into the sink, rinse each piece of oxtail under running water and scrub the pot clean of the grey residue before going on.
3. Return the rinsed oxtail to the clean pot with 1.5 litre of water, 3 crushed garlic cloves, 10 g of sliced ginger and 1 whole spring onion. Bring to the boil over high heat, then drop to the lowest simmer that still sends up a lazy bubble. Cook uncovered for 3 hours, skimming the surface every 20 minutes or so and topping up with boiling water so the bones always stay submerged. The broth should turn cloudy and milky as the marrow and collagen break down.