Line a large soup pot with the marrow bones. Layer the oxtail pieces and the soup meat on top.
Slice the ginger and roughly chop the unpeeled onion. Chop the carrots and leek. Add the vegetables and all the spices to the pot.
Fill up with four liters of water and season with fish sauce. Cook the soup slowly for about 4-5 hours. Then strain the soup. Put the soup in a cold place.
The next day it is easy to degrease because the fat has solidified as a solid layer on the surface and can be easily lifted off.
Arrange soy germ and cucumber cut into strips around the noodles. For the nuoc mam dip, finely chop and mix all ingredients together and serve with the soup.