Place the beef bones and onion halves on a baking tray and roast in a 220°C preheated oven.

After 45 minutes, remove the browned onion halves. Continue to roast the beef bones for another 15–20 minutes, or until browned.

In a large pot, add about 4L water. Add the roasted bones, browned onion, ginger, salt, star anise and fish sauce.

When the water boils, reduce the heat to low and simmer for about 6 hours.

Strain the broth. It is now ready to use to make pho noodle soup (or cool and refrigerate it for later use).

If using fresh rice noodles, prepare according to package directions. If using dried, soak according to package directions.

Divide the noodles among bowls.

Add the beef to the bowls.

Garnish with coriander and spring onion.

Pour the hot broth over the noodles and beef.

Serve immediately.