Blanch the beef bones in boiling water for 10 minutes. Drain, rinse and set aside.
Char the onion and ginger halves directly over a gas flame or under a hot broiler until blackened on the outside — this is essential for the flavour.
Toast the star anise, cloves, cinnamon, coriander seeds and cardamom in a dry pan for 1–2 minutes until fragrant.
Place the blanched bones, brisket, charred onion and ginger, and toasted spices in a large pot. Cover with 3 litres of cold water. Bring to a boil, skim any foam, then reduce to a very gentle simmer.
Simmer for 3 hours. Remove the brisket after 1.5 hours (when tender) and slice thinly. Strain the broth. Season with fish sauce, sugar and salt.
Divide the cooked noodles into bowls. Arrange sliced brisket and raw beef over the noodles. Ladle the very hot broth over — the hot broth will cook the raw beef.
Serve with bean sprouts, basil, coriander, spring onion, lime, chilli, hoisin and sriracha on the side.
