Soak dried mushrooms. Shred pork. Combine cornstarch, sherry & egg white; add to pork & toss to coat. Sprinkle with sesame oil. Shred bamboo shoots & soaked mushrooms. Mince scallion stalk. Blend cold stock & remaining cornstarch. Put remaining stock in a pan with mushrooms, bamboo shoots, soy sauce & salt. Bring to a boil. Reduce heat & simmer, covered, 2 to 3 minutes. Add cornstarch mixture & cook, stirring, until soup begins to thicken. Add pork & cook 1 minute more. Meanwhile beat eggs. Pour eggs in slowly, stirring constantly until they separate into shreds, then turn off heat. Sprinkle with minced scallions & pepper. VARIATION: For the pork, substitute chicken.