Thinly slice the pork fillets (or ask your butcher to do it for you). Crush the peppercorns in a pestle and mortar until fine, then rub all over the pork slices. Get your prep done up front: peel and finely grate the ginger, deseed and finely chop the chillies (to taste) and garlic, tear the mushrooms, and deseed and roughly chop the pepper. Trim and chop the spring onions and pak choi. Pick and finely chop the coriander leaves. Cook the noodles according to the packet instructions, then drain and briefly refresh under cold running water. Heat a wok and a frying pan over a high heat until screaming hot. Pour the sesame and sunflower oils into the hot wok, add the ginger, chilli and mushrooms and fry for 1 minute, or until slightly coloured. Throw in the pepper, spring onions, pak choi, garlic and beansprouts and stir-fry until wilted. Add the noodles, fish and oyster sauces, the coriander leaves and the stock and stir-fry for 2 to 3 minutes, or until the noodles are hot. Season taste with soy sauce. Meanwhile, drizzle a little sunflower oil into the hot frying pan and fry the pork for 2 minutes on each side, or until cooked through and golden. Serve up the noodle stir-fried noodles, top with the pork and tuck in.