If you are using dried mushrooms, soak them in warm water for 20 minutes. Drain, squeeze out any excess liquid and coarsely chop the mushroom caps and stalks.
Coarsely chop the carrots, celery and onions. Wash, cut and discard the green part of the leeks and coarsely chop the white portion. Peel the shallots but leave them whole.
Heat a large pan or wok over moderate heat and add the oil. Put in the spring onions, ginger, garlic and shallots, and stir-fry for 1 minute. Then add the carrots, celery, leeks and onions and continue to cook for 5 minutes. Put all the vegetables and the rest of the ingredients into a very large pan. Cover them with the cold water and bring to simmering point.
Using a large, flat spoon, skim off the foam as it rises to the top; this will take about 5 minutes. Heat the stock until it is almost boiling. Reduce the heat to moderate and simmer for about 2 hours.
Strain the stock through a large colander, then through a very fine mesh strainer. Leave to cool thoroughly. It is now ready to be used or transferred to containers and frozen for future use.
© 1995 Ken Hom. All rights reserved.