1. Soak dried mushrooms; reserve soaking liquid.
2. Shell and devein shrimp. Mince shrimp and garlic; then combine with cornstarch, sugar, soy sauce and salt. Beat egg; then blend in well. Form into walnut-size balls.
3. Bring water to a boil. Carefully drop in shrimp balls, a few at a time, and cook gently until they float (3 to 4 minutes). Drain, discarding liquid.
4. Meanwhile peel tomatoes and chop to a pulp. Dice pepper in i-inch squares. Cut celery stalks and scallions in i-inch sections. Crush remaining garlic. Slice soaked mushrooms.
5. Blend remaining cornstarch, soy sauce and sugar to a paste with the mushroom-soaking liquid.
6. Heat oil. Add remaining salt and garlic; stir-fry to brown lightly. Add green pepper, celery and mushrooms, and stir-fry a few times. Then cook, covered, 2 minutes over medium heat.
7. Add scallions and stir-fry until translucent (1 to 2 minutes more).
8. Add shrimp balls and tomato pulp; stir in to heat through.
9. Then stir in cornstarch mixture to thicken and serve at once.