Ingredients

2 cans (14.5 ounces each) reduced-sodium chicken broth

2 tablespoons soy sauce

1/4 to 1/2 teaspoon red pepper flakes

8 ounces fresh shitaki mushrooms, stemmed, caps thinly sliced (about 4 cups)

3 to 4 tablespoos rice vinegar

2 tablespoons cornstarch

1 large egg

1/2 package (7 ounces) firm tofu, cut into cubes and drained well

2 tablespoons finely grated peeled fresh ginger

Preparation

  1. In a large (5-quart) pot combine the broth, soy sauce, red pepper flakes, and 2 cups of water. Bring to a boil over medium heat. Add the mushrooms; reduce the heat, and simmer until tender, about 10 minutes.

  2. In a small bowl, whisk together 3 tablespoons of the vinegar and the cornstarch. Add to the pot; simmer, stirring, until the soup is thickened, about 1 minute.

  3. Add the egg through a slotted spoon and stir to form ribbons. Stir in the tofu. Remove from heat; let stand, covered, for 1 minute. Put the ginger in a small sieve, and squeeze to release its juice into the soup (discard the solids). Taste; add the remaining tablespoon of vineager, if desired.