Blanch the oxtail and beef bones in boiling water for 5 minutes. Drain and rinse.

Place the blanched bones in a large pot and cover with 2 liters of water. Bring to a boil, then reduce heat and simmer for at least 6 hours, skimming off any scum that rises to the surface.

Add the ginger and onion to the broth and continue to simmer for another hour.

Remove the bones and vegetables from the broth. Strain the broth through a fine-mesh sieve and discard the solids.

Place the brisket in the broth and simmer for 2-3 hours, or until tender.

Cook the rice noodles according to package directions. Drain and rinse.

Thinly slice the beef sirloin.

Divide the noodles among bowls. Top with sliced beef, brisket, and garnish with coriander, Thai basil, lime wedges, and chilli.

Season with fish sauce and sugar to taste.