Combine all the filling ingredients in a large bowl, and combine all the sauce ingredients in a small bowl. Heat wok over high heat, add peanut oil and swirl to coat wok. Add shrimp and vegetable mixture to wok and stir fry for 1 minute. Add garlic, ginger, and salt, and stir fry for another minute. Pour the reserved sauce over the vegetables, toss well to mix, and stir fry about 30 seconds. Remove from the heat, transfer to a bowl, and set aside to cool. (At this point, the filling can be covered and refrigerated for up to 1 day).
Drain filling of any excess liquid. Place the egg roll skins, one at a time so they don't dry out, on a flat surface. Arrange wrapper like a diamond with a corner facing you. Place about 1/4 cup of filling in the lower part of the diamond, leaving about 1 inch of wrapper on either side. Fold the bottom corner over the filling, roll up half way, then fold the sides over. Coat the top corner of the wrapper with egg, then seal and press to fully enclose. Arrange egg rolls on a baking sheet dusted with cornstarch, covered with a dry towel, until all the egg rolls are stuffed. (Do not refrigerate or the wrappers will crack.) Heat the peanut oil to deep-fry temperature (325 degrees F) in a wok or deep skillet. Fry the rolls until golden brown all over, about 2 minutes per side. Drain on paper towels and serve warm with Plum Sauce and Hot Mustard.
c.1997, M.S. Milliken & S. Feniger, all rights reserved