Heat a wok or heavy frying pan to a medium heat. Add the peppercorns (you can cook up to about 4 tablespoons at a time) and stir-fry them for about 5 minutes, until they brown slightly and start to smoke. Remove the pan from the heat and let them cool. Grind the peppercorns in a peppermill or clean coffee grinder, or with a mortar and pestle. Sift the ground peppercorns through a fine-mesh sieve and discard any of the hard hulls. Seal tightly in a screw-top jar to store. Alternatively, keep the whole roasted peppercorns in a well-sealed container and grind them when required.