Boil the noodles according to the packet instructions and drain. Heat the oil and fry the onions until soft. Add the beansprouts and long beans and fry for 1 minute over a high heat. Push aside and crack the eggs in to stir and cook through. Add the noddles, hoi sin sauce, soy sauce and pepper and continue to fry for 2 mintues. Sprinkle a little water all over to prevent drying out and stir for 1 minute more. Serve garnished with chopped spring onions or fresh coriander.