Susuru (udon noodle soup with chicken and sesame)

Method

1. To make the broth, put the chicken bones in a large pan. Boil a kettle, put the pan over a high heat, then pour the boiling water over to just cover the bones. Simmer for 10 seconds, then drain. Rinse the bones under cold running water – this removes impurities.
2. Clean the pan and return the chicken bones to it with the onion, carrot, spring onion, ginger and garlic. Pour in 2.2 litres water and bring to a gentle simmer, skimming off any scum that rises to the top, then continue to cook gently, uncovered, for 1½ hours. Set a large sieve over another large saucepan, then strain the stock into it – you should have about 1 litre stock.
3. Add the rest of the ingredients for the broth to the strained stock, then return to the heat and bring to the boil. Once boiling, remove from the heat and use a stick blender to whizz everything together until it’s emulsified and slightly thickened. Set aside to reheat before serving or leave to cool, then chill.
4. For the topping, put the chicken mince, sake, mirin and sesame oil in a medium saucepan. Put the pan over a high heat and stir-fry for 5 minutes, breaking up any clumps in the mince, until the chicken is cooked through. Turn the heat down to low-medium, stir in the rest of the ingredients and cook for another 5 minutes. Set aside to reheat before serving.
5. When you’re ready to serve, bring a large pan of water to the boil, set up a large bowl of iced water and gently reheat the broth and topping. Wash the sliced leek (if using) under cold running water for a few minutes to remove its astringency, then set aside to drain. Add the pak choi (if using) to the boiling water and cook for 2 minutes, then lift it out with a slotted spoon into the iced water. Once cool, squeeze dry with your hands, roughly chop and divide into 4 equal portions. Add the noodles to the water and cook for 8-10 minutes, then drain and add to the ice cold water to halt the cooking process.
6. Divide the noodles among bowls, then pour over the broth. Add the minced chicken on top with the pak choi alongside. Top with the leek (if using). Serve with crispy chilli oil, if you like.