Dried shiitake mushrooms provide depth of flavor and star anise lends its unique tangle of licorice, resin, and smokiness to this Asian-inspired split-pea soup. Ginger juice and watercress leaves offer bright finishes of taste and color to the soothing, familiar backdrop of split peas.
3/4 ounce dried shiitake
(about 10 small)
2 whole star anise
2 cups boiling water, plus 4 cups additional water
1 tablespoon peanut oil
5 scallions, thinly sliced (keep white and green parts separate)
1 cup finely diced onion
2 teaspoons minced garlic
1/4 cup dry sherry
1 1/2 cups split peas, picked over and rinsed
1/2 teaspoon salt
5 inches chunk fresh ginger (about 4 ounces)
2 to 3 cups loosely packed watercress leaves (from 1 average bunch)
1 to 3 tablespoons Japanese soy sauce (shoyu or tamari)
1 1/2 to 3 tablespoons Asian (toasted) sesame oil (optional)
1 tablespoon toasted black sesame seeds
, for garnish (optional)
Place the shiitake and star anise in a large glass measuring cup and pour the 2 cups boiling water over them. Cover and set aside unitl the mushrooms are tender enough to cut, usually about 10 minutes. Lift out mushrooms and star anise with a slotted spoon. Slice the caps thinly, discarding any stems (they are too woody to eat) as you go. Set the shiitake, star anise, and soaking liquid aside.
Heat the oil in a large soup pot. Add the white part of the sliced scallions, the onion, and the garlic, and cook over medium-high heat, stirring frequently, until they soften slightly, about 2 minutes. Add the sherry and cook over high heat, stirring constantly, until the sherry evaporates, about 30 seconds. Add the 4 cups of water, split peas, sliced shiitake, star anise (discard any broken pieces), and salt. Pour in the shiitake soaking liquid, taking care to leave behind any grit on the bottom of the cup.
Cover and bring to a boil. Cook at a gentle boil, stirring from time to time, until most of the peas have lost their shape, 50 to 60 minutes (or longer if the split peas are old and dried out). Taste the soup from time to time and remove the star anise if you feel it has given off sufficient flavor.
While the soup is cooking, prepare the ginger juice: Trim and grate the ginger. Once you have about a tablespoon, press the wad firmly between your fingertips and thumbs and collect the juice in a small bowl. Discard the ginger pulp. Continue grating ginger and expressing juice until you have 1 tablespoon of ginger juice. (The juice will look cloudy; some chunks of ginger are juicier than others, so you may have some ginger left over.) Set aside.
When the soup is done, remove the star anise "flowers." Stir well to dissolve the peas in the liquid and thicken the soup. For a creamier texture, purée part of the soup with a standard or immersion blender.
Just before serving, stir in the watercress and scallion greens. Add ginger juice, soy sauce, and toasted sesame oil (if using) to taste. Cook just until the watercress is wilted and tender, usually a matter of seconds. To serve, divide among 3 or 4 bowls and sprinkle with sesame seeds, if you wish.
If you own a pressure cooker, by all means use it to make this soup. Twelve minutes under pressure melts the split peas down into a purée.