In a large saucepan, melt the 2 Tbsp. of butter over medium high heat. Add the mushrooms to the butter and cook without stirring until mushrooms are deep golden brown - about 4 - 5 minutes. Flip mushrooms and continue to cook until golden brown. Remove mushrooms from the pan and set aside. Melt the remaining tablespoon of butter in the pan over medium heat and add the shallots and garlic, cooking until softened, about 5 minutes. Add mushrooms back to the pan and increase the heat to medium high. Add the sherry and cook, scraping up the bottom of the pan and cook until almost all the sherry has evaporated, about 3 minutes. Add the chestnuts, celery, thyme and stock. Bring to a boil, cover the pan and reduce to a simmer. Simmer for approximately 1 hour until chestnuts have softened. Let soup cool slightly and then puree in a food processor. - if the mixture is too thick, thin it down with a little vegetable stock. Return soup to the pan and re warm, seasoning with salt, pepper and the honey. Add the half and half and the remaining 2 Tbsp. sherry. Garnish with the cooked mushrooms, fresh thyme sprigs and a drizzle of truffle oil.

For garnish: In a small saute pan heat the 1 Tbsp. butter over medium high heat. Add the mushrooms and cook, without stirring for 3 - 4 minutes or until mushrooms are golden brown.