Place the beef bones, water, onions, ginger, star anise, cinnamon, peppercorns, cloves and coriander seeds in a large soup pot over high heat. Bring to boil, then decrease the heat to very low and simmer for 3 hrs, skimming the surface occasionally with a slotted spoon. The liquid should reduce by half.
Prepare the Slim Pasta Spaghetti as per package instructions (drained and rinsed). Cut spaghetti roughly in 5cm lengths with a kitchen scissors.
Remove from heat and strain through a fine mesh sieve into a clean pot. Remove and reserve any meat from the bones and discard the remaining solids.
Place the soup over high heat and bring to boil. Add the spaghetti, fish sauce and lime juice and stir to combine. Season with salt and pepper.
Place a few sliced beef and any reserved meat from bones into serving bowls. Ladle the soup into bowls, and top with bean sprouts, spring onions, chillies, mint and coriander, serve hot with lime wedges.