Step 1

Combine soy sauce, ginger, garlic, cornflour and sesame oil in a large bowl; add beef, mix well. Cover; refrigerate 1 hour.

Step 2

Meanwhile, using mortar and pestle, crush pepper medley and sichuan peppercorns finely.

Step 3

Heat half the peanut oil in wok; stir-fry beef, in batches, until browned.

Step 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.