In a small bowl, using the bottom of a glass or jar, crush the peppercorns into a coarse pulp. Stir in the coriander.
2.
Heat oil in a large wok or frying pan over medium high heat. Stir in beans, garlic, brown sugar, chilli, peppercorns and coriander. Stir-fry for 45 seconds. Pour in the water and cover to steam for about 2 minutes. Serve immediately.
Note:
If you can't find yard-long beans at your local Chinese or Asian market, substitute green beans.