In a food processor fitted with a steel blade, process the shrimp to a paste. Transfer to a large bowl; add the water chestnuts, seasonings, egg white, and cornstarch. Stir vigorously until a stiff paste forms. Chill thoroughly.
With a towel draped over the hand that holds a sharp knife, cut the noodles into 1/2-inch lengths. The towel prevents the noodles from flying around. Spread evenly on a cookie sheet.
Shape scant teaspoonfuls of the shrimp mixture into balls, then roll in the noodle pieces, pressing lightly to coat. Set on a cookie sheet.
Heat a wok or a deep skillet or saucepan until very hot. Add the oil and heat to 375 degrees. Deep-fry the shrimp balls in batches, turning them constantly, until golden brown, 3 to 4 minutes. Remove with a handled strainer or a slotted spoon, drain briefly in a colander, then transfer to paper towels. Between batches, skim the oil with a fine strainer, and reheat until hot. Serve the shrimp balls warm with sauce and mustard. To reheat, warm on a cookie sheet in a 375 degree oven about 10 minutes.