In a stock pot, on low heat sweat the onion, garlic,
celery and leek until tender (if using fresh truffle, slice and
add in this step).
Add the mushrooms and cook to wilt and release juices.
Reduce juice and deglaze with Madeira. Add the herbs.
Reduce Madeira and add mushroom stock or water (just
enough to cover contents of pot). Cook for 15 minutes and add
Take the pot off the heat. Remove the herbs and allow
soup to cool slightly.
Purée the soup while still warm and add cold diced
butter a piece at a time following with a slow drizzle of
truffle oil to emulsify.
Pass trough a fine mesh strainer. Adjust seasoning and
consistency with mushroom broth if needed. The finished soup
should be velvet smooth.
To garnish, serve a piece of good quality Parmesan cheese and a
drizzle of truffle oil or thinly sliced fresh truffle when in