Instructions

Prepare the Mushroom Broth
1. Set aside 4 medium shiitake mushrooms for garnish.
2. Stem the remaining mushrooms and cut the caps into quarters.
3. Combine the mushroom stems and dried shiitake mushrooms in a large saucepan with 1 ½ quarts of water.
4. Bring to a simmer, cover, and cook for 30 minutes over low heat.
5. Strain the broth through a cheesecloth, coffee filter, or paper towels into a bowl.
6. Squeeze the mushrooms over the strainer to extract as much liquid as possible. (Reserve the strained mushrooms for another use, such as a pâté.)

Cook the Vegetables
1. In a large, heavy soup pot, heat olive oil over medium heat.
2. Add shallots and cook, stirring, until tender, about 3 minutes.
3. Stir in garlic and cook for 30 seconds until fragrant.
4. Add quartered mushrooms and a generous pinch of salt.
5. Cook, stirring often, until the mushrooms are tender and release their juices, about 10 minutes.

Simmer the Soup
1. Pour in 2 tablespoons of sherry and the soy sauce, stirring to combine.
2. Add the mushroom broth, bouquet garni, and potatoes.
3. Bring to a simmer, cover, and cook for 1 hour.
4. Remove the bouquet garni and discard.

Blend the Soup
1. Using a blender, puree the soup in batches for a smooth, velvety texture. (Alternatively, use an immersion blender directly in the pot.)
2. Return the pureed soup to the pot and heat through.
3. Season to taste with salt and black pepper.
4. Stir in 1 more tablespoon of sherry, if desired.

Prepare the Garnish
1. Thinly slice the reserved 4 mushrooms.
2. Toss with lemon juice to enhance flavor and prevent browning.

Serve and Garnish
1. Ladle the soup into bowls.
2. Garnish with paper-thin mushroom slices, slivered sage, and chopped parsley.
3. Enjoy immediately or make ahead and reheat before serving.