IN A WOK OR SMALL SAUCEPAN heat the oil to 375F. Pull noodles apart into 4 small batches. Add 1 small handful at a time into the hot oil. They should puff within a few seconds. If they do not, the oil is not hot enough. With chopsticks or tongs, remove noodles and drain on paper towel. Repeat with the remaining noodles. Lightly crumble noodles. Makes about 4 cups. In a small bowl, blend thoroughly the mustard, water, sugar and salt; set aside for at least 10 minutes. Open the cavity of the roast chicken; pour out the juices and add them to any juices accompanying the chicken. Strain and degrease the juice. Mix 4 tablespoons of the strained juice with soy sauce, vinegar and sesame oil; set aside. Remove the chicken meat from the bones. Hand shred by tearing the meat into 1/4-by-2-inch-long shreds. Cut skin into 1 1/2-inch long thin slivers. In a large bowl mix together the skin, chicken and reserved mustard mixture. Add the green onions, coriander, sesame seeds and reserved roasting juice mixture; toss together like a salad. Just before serving, add lettuce and cashews; toss together. Arrange over a bed of crumbled rice stick noodles. Serve at room temperature.