Cook noodles, fresh or fried, until al dente. Drain and rinse in cool, then cold, water. Drain well. Sprinkle with vegetable, peanut or sesame oil. (Cold, oiled cooked noodles can be stored in the fridge for several days).
SAUCE: In a small skillet, heat vegetable oil and saute onions, garlic, ginger and chili peppers until garlic is soft but not brown. Turn off heat and add vinegar, soy sauce, sugar, sesame paste and chicken stock. Heat and simmer sauce, stirring for 2 minutes. Stir in sesame oil. Cool to room temperature. Pour sauce over chilled noodles and mix well. Heap noodles on s platter and garnish with sesame seeds, coriander and julienned vegetables.