Parboil the bones

• Place the beef oxtail and beef neck bones in a pot of water and bring to a boil.
• Strain the bones, then wash and clean them thoroughly to remove the gunk and gaminess.

Char the aromatics

• Char the yellow onion, ginger, cinnamon sticks, star anise and carrots.
• Cut the bottom end portion of the celery stalk and set aside.

Start the broth

• Add the water to a large pot and bring to a boil.
• Add the cleaned oxtail and beef neck bones.
• Add the charred ingredients and the celery stalk.

Season the broth

• Add the rock sugar.
• Add the chicken bouillon, fish sauce, beef paste and five spice seasoning tea bags.

Simmer and top up the broth

• After an hour, the broth will have reduced: add water to bring it back to its original level.
• Repeat with more water for the second hour, then remove the spice bag.
• Continue cooking; the meat will start to fall off the bone but not quite yet.

Continue simmering and skim the aromatics

• Top up with water again for the third hour and taste the broth.
• Fish out and remove the ginger, star anise and cinnamon sticks, as they will get mushy.
• Add more water for the fourth hour; the oxtail should now be fork tender.

Final gelatinous simmer

• For a more gelatinous, fall-off-the-bone oxtail, add a final amount of water and bring to a boil.
• Reduce the heat to low and simmer gently.

Cook the noodles and serve

• Cook the rice noodles according to the package instructions.
• Divide the noodles into bowls and add the desired proteins and condiments: sriracha, fried garlic, fried onions and chili oil.
• Top with cilantro, scallions and lime, then ladle the desired amount of broth into each bowl.