Hot and Sour Soup (Chinese)

6 cups fresh or canned chicken stock
1/2 cup thinly sliced bok choy or Napa cabbage
1 cup thinly sliced shitake, cloud ear,
    or other mushrooms
3 scallions (green onions, spring onions), green
    and white parts, thinly sliced
2 tablespoons soy sauce, or to taste
2 tablespoons finely chopped ginger root
2 tablespoons cornstarch
2 tablespoons water
6 to 8 ounces firm tofu, cut into thin strips
3/4 cup white vinegar, or to taste
2 teaspoons freshly-ground black pepper, or to taste
2 eggs, lightly beaten, or equivalent amount
    egg substitute
1 teaspoon toasted sesame oil

Bring the broth to a boil in a large saucepan and add the bok choy or cabbage, mushrooms, scallions, soy sauce, and ginger root.

Combine the cornstarch and water in a small bowl and stir into the broth when it returns to the boil. Boil for 3 minutes.

Add the tofu, vinegar, and pepper. Taste and adjust seasoning. Reduce the heat to a simmer and slowly drizzle the beaten eggs into the soup, stirring gently. Remove from the heat, add the sesame oil, and serve immediately.

Serves 6 to 8.