1/2 package (8 ounces) soft tofu, drained and cut into cubes
2 teaspoons soy sauce
1 teaspoon sesame oil
2 1/2 tablespoons cornstarch dissolved in 3 tablespoons water
1 egg white, beaten
Combine shrimp, scallops, and marinade ingredients in a bowl; stir to coat. Let stand for 10 minutes.
Place a saucepan over medium heat until hot. Add the oil, swirling to coat sides. Add ginger, shrimp, and scallops; stir-fry for 1 minute. Add chicken broth; bring to a boil. Add straw mushrooms, peas, tomato, tofu, and seasonings; cook for 1 to 2 minutes. Add cornstarch solution; cook, stirring, until soup thickens. Reduce heat to low; slowly drizzle in egg white, cook, stirring constantly, until egg white sets. Pour into a soup tureen and serve.