There are two versions of the origin of this name. "Dan Dan" is onomatopoetic for "clap clap" and supposedly refers to the noise made by street vendors in Szechuan as they hawk this tasty snack. Dandan are wooden buckets, one on each end of a pole carried across the shoulders, from which vendors sell Dan Dan Mein in the streets of Chengdu. This recipe is adapted from Mrs Chiang's Szechuan Cookbook. It calls for Szechuan peppercorns, called "huajiao" ("flower pepper") in Chinese, and these are what give Szechuan food its distinctive taste. They can be found in Chinese specialty groceries. Do not substitute with black peppercorns, cayenne pepper or red chili peppers. Furthermore, do not substitute Middle Eastern tahini paste for the rich Chinese toasted sesame paste. The two are not interchangeable, although peanut butter is an acceptable alternative in this recipe. For the hot chili oil, use a commercial brand, mince any good dried red chilies, or make you own as follows.