Add Sichuan peppercorns to a small frying pan and toast over medium heat for 1-2 minutes. Remove to a mortar and pestle and grind. Add ginger and garlic, pounding until a smooth paste has formed.
Combine the chicken stock, soy, cooking wine, chilli paste, cornflour and sugar, mixing until smooth, set aside.
Heat half the oil in a large frying pan or wok over high heat. Add pork in batches cooking until seared all over. Set aside.
Heat remaining oil in the pan and add the Sichuan pepper paste, cooking over medium heat for 1 minute until fragrant. Increase heat and stir in mushrooms and beans, tossing well. Cook for 2 minutes then pours in soy mixture with the pork. Continue cooking a further 2-3 minutes until beans are tender and pork is just cooked through.
Serve pork with steamed rice or thick rice noodles.