Place beef and/or bones in a large stock pot and cover with cold water. Cover and bring to the boil. Boil rapidly for 5 mins and then remove bones and rinse them in a colander. Pour away water and clean stock pot thoroughly. (This steps removes impurities and ensures a clear soup).
Place meat/bones back into stock pot and cover with water. Place on a medium heat.
Toast all of the dried spices in a dry frying pan until fragrant (2-3 mins) and then lightly crush in a pestle and morter. Wrap in muslin, secure and place into stock pot.
Add sliced ginger and bruise lemongrass stalks before adding to stock pot.
Blacken onions under a hot grill and then add.
Bring to boil, turn down to barely simmering and simmer uncovered for at least 5 hours.
Strain and reserve the cooking liquid. Can retain any oxtail or shin meat for the soup and discard the remainder of the stock pot ingredients.
Strain the liquid through a muslin cloth into a large sauce pan. Add sugar, 2 tblsp fish sauce and salt to taste.
To assemble: add cooked noodles, beansprouts and finely sliced raw steak to a deep noodle bowl. Pour over boiling hot stock (this will just cook the steak).
Add the sliced chilli, spring onion and fresh herbs. Add fish sauce, soy sauce, sesame oil and freshly squeezed lime juice to taste.