Hot and Sour Cantonese Soup

6 ounces extra-firm tofu, drained4 tablespoons good quality soy sauce, divided1 teaspoon oriental sesame oil3 1/2 tablespoons cornstarch, divided6 ounces pork tenderloin cut into 1 inch by 1/8-inch matchsticks3 1/2 tablespoons cold water1 large egg5 cups fat-free, lower sodium chicken broth 1/2 can (20 ounces) water-packed stripped bamboo shoots, drained2 cans (4 ounces) mushroom pieces and stems1 tablespoon red wine vinegar (see note)1 tablespoon balsamic vinegar (see note) 1/2-1 teaspoon cayenne pepper1 teaspoon ground white pepper3 medium green onions, green parts only, thinly slicedPlace tofu block on a dinner plate, place another dinner plate on top of tofu and weigh plate down with a large, unopened can. After 15 minutes tofu should have released about 1/2 cup of clear liquid.In medium bowl whisk together 1 tablespoon soy sauce, sesame oil and 1/2 tablespoon cornstarch; stir pork into marinade and set aside for 10 and no more than 30 minutes.In a small bowl, stir 3 tablespoons cornstarch together with 3 tablespoons water and mix well; set aside.In small bowl mix remaining 1/2 tablespoon cornstarch, remaining 1/2 tablespoon water and egg until combined. Set aside.In a large saucepan over medium-high heat, bring chicken broth to a boil. Reduce heat to medium-low; add bamboo shoots and mushrooms (including liquid), and simmer about 5 minutes. While broth simmers, drain tofu and pat dry with a paper towel; dice tofu into Ø-inch cubes. Add tofu and pork, including marinade, to soup, separating any stuck together pork pieces. Simmer until pork is no longer pink, about 2 minutes.Stir cornstarch mixture and stir into soup. Increase heat to medium-high, cook, stirring occasionally, until soup thickens, about 1 minute. Stir in vinegars, cayenne and white peppers, and remaining 3 tablespoons soy sauce; turn off heat.Using a large spoon, slowly pour a very thin stream of egg mixture into pot in a circular motion. Let soup sit 2 minutes. Gently stir soup once to distribute egg; ladle into bowls and top with green onions.Serves six as a first course.Cook's note: For better flavor, omit red wine and balsamic vinegars and use 5 tablespoons Chinese black vinegar (available in all Asian markets).Nutrition values per serving: 110 calories (25.4 percent from fat), 3.1 g fat (0.7 g saturated fat), 8.8 g carbohydrates, 1.7 g fiber, 11.3 g protein, 54 mg cholesterol, 687 mg sodium.