PREPARE AHEAD: In a small bowl, cover the mushrooms with 1/2 cup of warm water and let them soak for 30 minutes. Discard the water.

 

With a cleaver or knife, cut away and discard the tough stems of the mushrooms, and shred the caps by placing one at a time on a chopping board. Cut them horizontally into paper-thin slices, and then into thin strips.

 

Drain the pieces of bamboo shoots and bean curd, and rinse them in cold water. Shred them as fine as the mushrooms.

 

With a cleaver or sharp knife, trim the pork of all fat. Then shred it by slicing the meat as thin as possible and cutting the slices into narrow strips about 1-1/2" to 2" long.

 

Have the above ingredients, stock, salt, soy sauce, pepper, vinegar, cornstarch mixture, egg, sesame-seed oil and scallions within easy reach.

 

TO COOK: Combine in a heavy 3-qt saucepan the stock, salt, soy sauce, mushrooms, bamboo shoots and pork. Bring to a boil over high heat, then immediately reduce the heat to low, over the pan and simmer for 3 minutes.

 

Drop in the bean curd, and the pepper and vinegar. Bring to a boil again.

 

Give the cornstarch mixture a stir to recombine tie and slowly pour in the beaten egg, stirring gently all the while.

 

Remove the soup from the heat and ladle it into a tureen or serving bowl. Stir in the sesame-seed oil and sprinkle the top with scallions. Serve at once.

 

Yields: 4 to 6 servings.