Shake the dried mushrooms in a sieve to loosen the dirt.
Heat the oil in a soup pot. Add the onion, carrots, and celery and saute over medium high heat, stirring occasionally, until the onion is well browned, about 15 minutes.
Scrape the bottom of the pan to loosen the juices that have collected there, then add the dried mushrooms and their soaking liquid, the remaining ingredients, including the boquet garni, and 9 cups water. Bring to a boil, then lower the heat and simmer, partially covered, for 45 minutes. Strain.
To make the boquet garni:.
You may put them into the broth whole or gather them in a cheesecloth bag and tie with a string. If you put them in loose, just fish them when done making stock.