it is one of the classical dishes of guangzhou. the procedure is as follows: clean the pork kidney (foreleg), cut it into pieces and boil them thoroughly. let them stay in the running spring water for one whole day. then boil them with sugar, white vinegar, and salt. after boiling, let it cool down and wait for several hours before it can be served. because the spring water is from bai yun mountain, the dish is named bai yun sweet and sour pork kidney. this dish is sweet sour, fatty but no greasy, crisp-skinned. your will never be tired of tasting it. while cooked, this dish is paid attention to its colors, flavors, taste and the presentation. if some herbs and red pepper shreds are added, it will be a delight to eyes and be tastier.