Chilled buckwheat noodle soup (naengmyeon)

Instructions

1. To make the beef broth, combine all the ingredients in a large stockpot. Add 3 litres (101 fl oz/12 cups) water and bring to the boil over high heat. Skim off any impurities that rise to the surface, then reduce the heat to medium–low. Cover with a lid (leaving it slightly ajar) and simmer for 1 hour or until the beef is tender. Remove the beef from the stock and allow the beef and stock to cool to room temperature. Wrap the beef in plastic wrap and chill in the refrigerator for at least 4 hours, or preferably overnight.
2. Strain the broth through a fine-mesh sieve into a large airtight container. Add all the ingredients for the soup base and stir until the sugar has dissolved. The soup should taste sharp, tart and mildly sweet. Taste and adjust the seasoning if necessary. Seal the container with a lid, and transfer to the refrigerator to chill for at least 4 hours, or preferably overnight. To speed up the chilling process, you can place the stock in the freezer for 1–2 hours, until it becomes slushy but not frozen.
3. To make the pickled cucumber, cut the cucumber in half lengthways then slice each half on an angle into 3 mm (⅛ in) thick slices. Transfer to a bowl, then add the salt and sugar. Toss to combine, leave to sit for 10 minutes, then add the vinegar and mix well. Refrigerate until ready to use.
4. For the pickled radishes, thinly slice the radish then stack the slices up and cut into 2 cm (¾ in) wide strips. Transfer to a bowl, then add the salt and sugar. Toss to combine, leave to sit for 10 minutes, then add the vinegar and mix well. Refrigerate until ready to use.
5. Take the beef out of the refrigerator and slice it thinly against the grain.
6. Cook the buckwheat noodles according to the packet instructions. Prepare an ice bath while the noodles are cooking. Once cooked, drain the noodles and immediately plunge them into the iced water to stop the cooking process. Drain, and divide the noodles among four bowls.
7. To each bowl, add some pickled cucumber and radish, a few slices of beef and half a boiled egg. Divide the chilled soup among the bowls. Serve cold with hot mustard.