The concrete walk-ups contain basic homes filled largely with elderly residents who remember when Chongqing was a different place. It is the elderly, still at home in the middle of the afternoon, who are first out on the street when they hear the calls of the bangbang woman.

A bangbang woman, or man, is someone who earns a living from the bamboo pole they wear over their shoulder. Men add rope to their bamboo pole and carry out day labour, sometimes helping on building sites and other times waiting outside department stores to offer assistance to shoppers carrying newly purchased washing machines and other white goods to their cars.

The woman shouting the names of her dishes has two buckets draped from her bamboo pole: one contains cold wheat noodles, rice noodles, and chunks made from rice starch; the other contains the various ingredients required to whip those ingredients into a delicious dish.

Both (made from rice starch) and (made with wheat noodles) use a similar base and, when mixed together by the customer, offer something cool in the mid-summer heat. In Chongqing, that coolness still comes with plenty of raw, chopped chillies as the base.

(sour and spicy rice noodles) stands by itself in this category. It's served hot and, unlike the other two dishes, comes in a soup instead of relying on chilli oil to lubricate the noodles. relies on its sour taste that comes from the addition of extra vinegar, not to mention plenty of coriander, to deliver refreshment. This is not to suggest the dish is not spicy; its broth is dark red in colour, thanks to a base of mashed chilli peppers.

"and are the most popular two summer dishes in Chongqing," says Jiang, a street vendor who sells hers outside a hospital in Shapingba, Chongqing's traditional student district. When pushed on the question of which of the three dishes is most popular, Jiang says that it is impossible to say.

"has more [the mouth-numbing sensation that comes from the Sichuan peppercorns]; has more [spice]," she says, adding that different people opt for different tastes. "Some people even choose not to add any spices at all," she says, although the majority will happily let her add chillies to their dish.

Making is a very fast process indeed. The cold fen are placed into the plastic bowl that will be served to the customer, and it is then a case of adding myriad ingredients that add such complexity to the simple jelly-like starch. Typically these include soy sauce and vinegar, salt, MSG, ground Sichuan peppercorn, chilli paste, preserved vegetables and peanuts. Finely chopped spring onion is typically sprinkled on the top.

" , or perhaps , are my favourite dishes to eat on a really hot day," says Coco Huang Xingyuan, originally from Jiangxi province, but who works as a legal assistant in Chongqing. " and are cold dishes, which is good to eat when the weather is hot; is in a hot soup, so I don't go for this on really hot days."

Making requires the same process but with two crucial differences. Apart from the difference in the noodle (is made with typical wheat noodle rather than rice noodles) this dish also includes sugar and, as Jiang explains, has a flavour that concentrates more on red chillies and less on ground Sichuan peppercorns that can leave the mouth numb.

Wei Wei, a graphic designer who has lived in Chongqing for several years, and who is originally from Yibin, Sichuan, a place famous already for having some of the spiciest noodles in the region, explains that her favourite of the three dishes is the wheat noodle-based . "Chongqing summers are so hot," Wei says. "is the best dish to eat if you want to cool down."

For Wei, the spicy nature of the dish, compounded with the heat of the summer, is not an issue. "My other favourites, hotpot or traditional local dishes, are all served hot, and they are spicy too," she says. "is spicy, but it's served cool. And compared to other food in Chongqing and Sichuan, it's not actually the spiciest dish around."

, a popular summer dish thanks to its surprisingly refreshing nature, is the least convenient to find. Because of the hot broth required to make the dish, it is less commonly carried through populated areas by bangbang women, and it is more likely to be found in small shopfront establishments in commercial centres.

Small restaurants serve to diners, who perch on plastic stools outside, although some have space indoors for just a few seats. The dish is made by first making a chicken or pork broth in which the rice noodles are cooked to order.

Meanwhile the customer's bowl is filled with a selection of peanuts, fried soy beans, vinegar, soy sauce, chilli oil, sesame oil and sugar. Once the noodles are ready, they're placed in the bowl and some of the broth is added. Coriander tops the finished dish, as much for colour as to add complexity to the flavour.

The idea of eating spicy food on a hot day may appear counterintuitive to those not used to an environment in which spices influence almost every dish.

But Huang says that eating spicy dishes at the hottest times of the hottest days of summer is not a recipe for discomfort.

"Eating such spicy food in the heat does make you sweat a bit, but it's not uncomfortable," she says. "Normally, I like to add plenty of vinegar, and I add even more in the summer. It gives it a refreshing kick, which is what you need when the weather is pushing 40!"

Where to find it

The bangbang vendor can often be found at Songlin Lu, Chongqing University Campus A, Shapingba, Chongqing.

Jiang works outside the hospital at Xiaolongkan Xinjie, Shapingba, Chongqing.

The most famous suan la fen shop in Chongqing is Lao Nong Min, Three Gorges Square, Shapingba, Chongqing.