In this popular Cantonese teahouse specialty, the rice noodles are permeated with an aromatic infusion of curry spices and herbs, seasonings borrowed from Indian and Malay cooking-- both cuisines are indigenous to Singapore. Cover mushrooms with warm water. When soft and pliable, remove and squeeze dry. Cut off and discard stems. Cut caps into thin slices. Bring a large pot of water to a boil. Add noodles; using chopsticks, stir and loosen noodles. When soft and pliable, about 30 seconds, drain them into a colander. Cover and let cool. Preheat wok until hot. Add 2 tablespoons of the oil, 1 slice of the ginger, the chicken, shrimp and pork; stir-fry until shrimp and chicken feel firm to the touch, about 1 minute. Remove and set aside. Pick out and discard ginger. To hot wok add remaining oil, ginger and salt, crushing ginger against sides of wok. When oil is hot, toss in onions, celery, snow peas, mushrooms, bell pepper and green onion; stir- fry until tender and crisp (1 to 2 minutes). Push vegetables to side of wok. Add curry powder to center of wok and lightly saute for 10 seconds. Then add sugar, soy sauce and chicken stock. Mix. Add noodles; combine,with vegetables by using chopsticks, to lift, shake and separate strands of noodles, until they are evenly coated with sauce, moist but not wet and begin to cling to each other. (Add more chicken stock if noodles seem too dry). Return meat mix mixture, taste for seasoning. Toss to heat through. PER SERVING: 665 calories, 46 g protein, 61 g carbohydrate, 26 g fat (7 g saturated&4, 151 mg cholesterol, 146 mg sodium, 5 g fiber. Joyce Jue writing in the San Francisco Chronicle, 8/7/91.