Slice the mushrooms and sauté with celery, onion, shallot and garlic in the truffle oil. Once the vegetables are tender, add the wine, and cook until the wine is almost completely dissolved. Add the stock, thyme, porcini powder, sherry vinegar, cream and half-and-half. Bring to a low simmer.
Cook for about an hour until the flavors and aroma deepen. Season with salt and pepper to taste. Puree the mix in the blender. (Remove thyme sprigs if desired. Be careful with the hot liquid.) Strain the puree for more silky texture.