COMBINE THE PORK, SOY SAUCE and salt in a small bowl and mix well. Heat a wok or saute pan until it is hot. Add the oil and deep-fry the pork, stirring with a spatula to break it into small pieces. When the pork is crispy and dry, about 4 minutes, remove it with a slotted spoon and drain on paper towels. Pour off the oil, leaving 2 tablespoons in the wok. Reheat the wok and add the garlic, ginger and scallions, and stir-fry for 30 seconds. Then add the sesame paste, soy sauce, chili oil, salt and chicken stock and simmer for 4 minutes. Cook the noodles in a large pot of boiling water for 2 minutes if they are fresh or 5 minutes if they are dried. Drain the noodles well in a colander. Divide them into individual bowls or put in large soup tureen. Ladle on the sauce.