La zi yu is a dish designed to scare the living hell out of people with an aversion to spicy food. The dish is a Sichuan fish broth topped with a thick layer of chilli oil and Sichuan pepper. When presented on the table, the soup appears to be nothing more than a pile of dried chillies swimming in a thick layer of lurid red oil that obscures all that lies beneath. It is perfect winter eating because there is no escape from the abounding heat of the dish.

Great skill lies in retrieving the submerged chunks of flaky, filleted fish whilst leaving behind the bulk of the oil and whole spices; managing the numbing and burning sensations of the chilli and Sichuan peppers so that they build to a slow crescendo of pain as the meal ends.

Drinking the oily soup is a special kind of madness.

Chilli and Sichuan peppers are probably the only foods that people eat to experience pain. For some, pain is not a sensation that is seen as a positive outcome of eating and is more associated with overeating or just eating bad food. The attractions of pain from chilli are obvious and well documented: making you feel hotter, inducing sweat, increasing metabolism, reducing hunger and the warm endorphin rush of survival. The payoffs are obvious to the chilli lover.

The effects of Sichuan pepper are less familiar. Sichuan pepper is the outer pod of a tiny fruit from a tree in the citrus family. It is no relative to your regular, run-of-the-mill pepper at all nor is it related to chillies. It is one of a handful of foods that you eat for the sensation of eating it as much as you would eat it for the flavour alone and the sensation, at least in a food, has no parallels. Sichuan pepper produces a numbing reaction on the tongue similar to licking on a nine-volt battery; a physical feeling of tingling or buzzing.

Until a few years ago, the reasons behind this sensation were unknown. This research published in Nature Neuroscience in 2008 identified that the active ingredient in the pepper (hydroxy-alpha-sanshool, for you budding biochemists) acts on the neurons that are associated with proprioception (your bodies own sense of where it is) and the detection of touch or vibration. It’s a food that cons your mind into sensing something ever so slightly unreal.