The owner of this tiny restaurant, Wang Guixi, of Liuzhou, Guangxi Zhuang autonomous region, from which luosifen comes, boasts of snail noodles that he says turn up the pungency full volume, unlike other Beijing providers of luosifen who feel the smellometer needs to go in the other direction in deference to local noses and palates.

But rather than being driven away by Wang's take-it-or-leave-it approach to preparing luosifen, his noodles are sold out every day and he often closes his doors early in the afternoon.

"Most people only know that snail noodles have a pungent smell, but authentic snail noodles have to be refreshing, spicy and hot at the same time," he says. "Of course, we always subconsciously compare which restaurant is better, but you should not overlook the fact that the snail meat and sour bamboo shoots, the two essential toppings for snail noodles, are the criteria you need to consider first.

"In producing sour bamboo shoots you first need to select the big meaty and attractive bamboo shoots, supplemented with spring water specially drawn from the mountain, and finally kept in a large earthen jar for a couple of weeks. This is how the smell of pickled bamboo shoots can stimulate diners' taste buds."