Doganitang

Method

1. Put 350 g of ox knee cartilage in a bowl, cover generously with cold water and soak for 3 hours in a cool place, changing the water twice. The water should run pink rather than red by the end; this is what keeps the finished broth clean-tasting.
2. Drain the bones, put them in a deep pot, cover with fresh cold water and bring to a hard boil over high heat. Boil for 10 minutes, then tip everything into the sink, rinse each piece under cold running water to remove the grey scum, and scrub out the pot.
3. Return the bones to the clean pot with 1.5 l of water, 0.5 onion, 3 cloves garlic cloves, 10 g of sliced ginger, 1 spring onion cut into lengths and 0.5 tsp of black peppercorns. Bring to the boil uncovered over high heat.