Don't throw out the asparagus stalks. Instead, simmer them in the chicken broth for extra flavor.

1 pound asparagus, tough stems snapped off and reserved, stalks cut into 1/2-inch lengths
4 cups chicken stock, preferably homemade, or use low-sodium canned
1 cup boiling water
1 cup (1 ounce) dried porcini mushrooms, rinsed in cold water to remove grit
2 tablespoons unsalted butter
1/2 cup minced shallots
1 pound shiitake mushrooms, stems discarded, caps sliced into 1/4-inch thick strips
1/4 cup vintage or tawny port
1/2 teaspoon dried tarragon
3 tablespoons all-purpose flour
1/2 teaspoon salt
1/4 teaspoon freshly ground pepper
1/2 cup sour cream, at room temperature, for garnish
2 tablespoons chopped fresh parsley, for garnish

1. In a medium saucepan, bring the broth and asparagus stems to a boil over high heat. Reduce the heat to low and simmer until the stems are very tender, about 20 minutes. Strain, discarding the stems, and set aside.

2. In a small bowl, pour the boiling water over porcini; let stand until the mushrooms are softened, about 30 minutes. Lift out the mushrooms and chop coarsely; set aside. Pour the soaking liquid through a cheesecloth-lined strainer into a bowl and set aside.

3. In a soup pot, melt the butter over medium heat. Add the shallots and cook, stirring often, until softened, about 2 minutes. Increase the heat to medium-high and add the shiitakes, regular mushrooms and soaked porcini. Cover and cook for 5 minutes. Uncover, and cook, stirring often, until the mushrooms have given off their liquid, it evaporates, and they begin to brown, about 7 minutes. Add the port and tarragon and boil until port is almost evaporated, about 2 minutes.

4. Reduce the heat to low, sprinkle the flour over vegetables and stir for 1 minute. Stir in the broth, mushroom soaking liquid and asparagus, scraping up any flour on the bottom of the pot with a wooden spoon. Bring to a simmer and cook, partially covered, until the asparagus is tender, about 8 minutes. (The soup can be prepared up to 2 days ahead, cooled, covered and refrigerated. Reheat slowly, stirring often, over low heat until hot.) Ladle the soup into individual soup bowls, garnishing each serving with a dollop of sour cream and a sprinkle of parsley. Serve hot.