1.Combine soy sauce, ginger, garlic, cornflour and sesame oil in a large bowl; add beef, mix well. Cover; refrigerate 1 hour.
2.Meanwhile, using mortar and pestle, crush pepper medley and sichuan peppercorns finely.
3.Heat half the peanut oil in wok; stir-fry beef, in batches, until browned.
4.Heat remaining oil in wok; stir-fry brown onion, beans and pepper mixture until onion is tender. Return beef to wok with wine, the water and oyster sauce; bring to the boil. Stir-fry until beans are cooked. Remove from heat; stir in green onion.
Pepper medley is a mixture of black, white, green and pink peppercorns, coriander seeds and allspice, sold in grinders in supermarkets. You can use your own blend of various peppercorns, if you prefer. Not suitable to freeze or microwave.