1. In a small bowl combine mushrooms and enough water to cover, stand 15 minutes then drain
In a large saucepan bring stock, soy sauce, chili garlic sauce, vinegar, sesame oil and ginger to a boil, add all but cornstarch and water and egg and simmer about 15 minutes.
Dissolve cornstarch in water, add ¼ cup the hot soup liquid and then pour back into pan.
Stir constantly until mixture thickens, about 1 minute. Drizzle with egg, serve immediately