The sheer variety of tantanmen in Tokyo reveals just how far this noodle dish has traveled from its Sichuan roots. Once sold by walking street vendors carrying their noodles and sauces in baskets attached to poles, there are now nearly as many interpretations of dandan noodles as there are restaurants.
Traditionally, the noodles are dressed in a spicy sauce containing preserved vegetables, chili oil, Sichuan pepper, minced pork and scallions. Many chefs include sesame paste or peanut butter; Shanghainese or American Chinese styles tend to be sweeter, with greater emphasis on nuttiness over spiciness. In Japan, tantanmen seems loosely defined, a chance to innovate; in some renditions, merely adding sesame paste is enough to call it tantanmen.
Broadly speaking, there are two categories of tantanmen: shiruari (soup) and shirunashi (soupless). Both styles have their own merits, but I find the latter more to my taste — the textural integrity of the noodles is better preserved with a mere slick of sauce, rather than softening in hot soup; the spices come through with greater clarity without the dilutive distractions of broth.