About 30 minutes ahead of time, rinse and drain the mung bean sprouts to give them time to dry thoroughly. Soak the Chinese dried mushrooms in warm water to soften (20 to 30 minutes). Squeeze any excess water out of the mushrooms and thinly slice. Dice the red bell pepper. Grate the carrot and finely slice the bamboo shoots. In a small bowl, combine the oyster sauce, chicken broth or water, soy sauce and sugar. Set aside.
Heat 2 tablespoons in a frying pan, swirling so that it coats the pan. When the oil is sizzling, stir-fry the vegetables, starting with the dried mushrooms and then the bamboo shoots, bell pepper, mung bean sprouts and grated carrot. Taste and season with salt and/or freshly ground pepper if desired. Remove from the heat and cool.
. Lay a wrapper in front of you so that it forms a diamond shape. Brush the edges of the wrapper with the lightly beaten egg. Place 2 tablespoons of filling in the bottom half, spreading it out sideways to form a rectangle shape but not touching the edges. Lift the bottom corner of the wrapper and tuck it in under the filling. Fold over the left and right sides of the spring roll wrapper. Continue rolling up the wrapper. When you are almost finished, lightly brush the edges of the top corner of the diamond with the beaten egg mixture, fold over and seal.
Heat oil for deep-frying to 360 degrees Fahrenheit. When the oil is ready, carefully add the spring rolls, a few at a time, cooking until they are golden brown and crispy (3 to 4 minutes). Remove and drain on paper towels. Serve with plum sauce, hot mustard, or sweet and sour sauce. Yields 18 - 20 spring rolls.