Heat the olive oil in a large saucepan. Add the celery, onion, and carrot and cook over medium-low heat for about 5 minutes until soft. Add the mushrooms and continue to cook until the mushrooms are tender and lightly browned. Add the garlic and cook for another couple of minutes until the garlic releases its aroma.

Add the chestnuts and about 4 cups of broth and simmer over medium-low heat for about 30 minutes, adding additional broth if needed. Season with salt and pepper. Cool for 15 minutes and then puree until thick and smooth. Serve just warm with your garnish of choice.

Note: To garnish the soup, you could saute some fresh mushrooms and some diced pancetta, a spoonful of pesto, or add a dollop of sour cream with fresh chopped herbs. I wanted to simply enjoy the flavor on its own, so I simply topped the soup with some chopped fresh chives, a drizzle of really good extra virgin olive oil, and some cracked black pepper. This is one soup in particular that is best not served too hot. Served just warm, the flavor is much more pronounced.