Vietnamese beef soup

Method

1. First, make the stock. Preheat the oven to 200°C/fan180°C/gas 6. Put the bone, onion, garlic and ginger in a roasting tray and cook for 1 hour.
2. Transfer to a large pan and add 2.5 litres cold water. Add the cinnamon, cloves and lemongrass or zest and bring to a simmer on the hob. Cook for 2 hours, then strain into a bowl, discarding the solids – you should have about 1 litre. Season with the fish sauce, salt and sugar. Ideally, cool overnight, then skim any fat from the top.
3. To make the final dish, cook the noodles in plenty of boiling water for 2 minutes, until just tender. Drain, cool under cold running water and divide the noodles between bowls.
4. Put the stock into a large wok or pan and heat until simmering. Add the Chinese greens. Thinly slice the steaks, add to the pan and remove from the heat – this means the steak is only just cooked and very tender.
5. Divide the soup between the bowls of noodles, then top with the spring onions. The beansprouts, chillies, limes and herbs are served at the table, with extra fish sauce. Each diner wilts the herbs and beansprouts into the broth, then tempers it with lime juice, chillies and fish sauce.