Creamy Mushroom Soup

6 tablespoons unsalted butter
6 large shallots , minced (about 3/4 cup)
2 small cloves garlic , minced (about 1 1/2 teaspoons)
1/2 teaspoon ground nutmeg , freshly grated
2 pounds white button mushrooms , wiped clean and sliced 1/4 inch thick
3 1/2 cups chicken stock or canned low-sodium chicken broth
4 cups hot water
1/2 ounce dried porcini mushrooms , rinsed well
1/3 cup dry sherry or Madeira
1 cup heavy cream
2 teaspoons lemon juice from 1 lemon
Table salt and ground black pepper

Sauteed Wild Mushroom Garnish (optional)
2 tablespoons unsalted butter
8 ounces shiitake mushrooms or chanterelle, oyster, or cremini mushrooms, stems trimmed and discarded, mushrooms wiped clean and sliced thin
Table salt and ground black pepper
Instructions

      1. Melt butter in large, heavy-bottomed Dutch oven over medium-low heat; when foaming subsides, add shallots and saute, stirring frequently, until softened, about 4 minutes. Stir in garlic and nutmeg; cook until fragrant, about 1 minute longer. Increase heat to medium; add sliced mushrooms and stir to coat with butter. Cook, stirring occasionally, until mushrooms release liquid, about 7 minutes. Reduce heat to medium-low, cover pot, and cook, stirring occasionally, until softened and mushrooms have released all liquid, about 20 minutes. Add chicken stock, water, and porcini mushrooms; cover and bring to simmer, then reduce heat to low and simmer until mushrooms are fully tender, about 20 minutes longer.

      2. Pour soup into a large bowl. Rinse and dry Dutch oven. Puree soup in batches in blender until smooth, filling blender jar only halfway for each batch. Return soup to Dutch oven; stir in Madeira and cream and bring to simmer over low heat. Add lemon juice, season to taste with salt and pepper, and serve with sauteed mushroom garnish, if desired. (Can be cooled to room temperature and refrigerated up to 4 days.) If making ahead, add cream at serving time.

      3. For the Sauteed Wild Mushroom Garnish (optional):
      Heat butter in medium skillet over low heat; when foam subsides, add mushrooms and sprinkle with salt and pepper. Cover and cook, stirring occasionally, until mushrooms release their liquid, about 10 minutes for shiitakes and chanterelles, about 5 minutes for oysters, and about 9 minutes for cremini. Uncover and continue to cook, stirring occasionally, until liquid released by mushrooms has evaporated and mushrooms are browned, about 2 minutes for shiitakes, about 3 minutes for chanterelles, and about 2 minutes for oysters and cremini. Sprinkle a portion of mushrooms over individual bowls of soup and serve.