Pour chicken broth into a 3-quart saucepan.

Place saucepan over medium heat and bring to a light simmer.

Add soy sauce, mushrooms, chili-garlic sauce and white pepper. Continue to simmer for 5 more minutes.

In a cup or small bowl, combine cornstarch with cold water.. Stir until mixture is smooth. Add cornstarch mixture to hot soup and stir well. Simmer for 3 or 4 more minutes, until soup is thickened.

In another cup or small bowl, beat egg until yolk and white are combined. Pour beaten egg slowly, in a fine stream, into soup. Stir soup slowly several times. Stop stirring and wait 30 seconds for egg to cook.

Add tofu strips and green onions to soup. Stir well.

Remove from heat. Add distilled white vinegar and sesame oil. Stir a few times.

Serve hot.