Sichuan peppercorn

The dried husk of Zanthoxylum, not a pepper and not related to one. The numbing is hydroxy-alpha-sanshool, an unsaturated fatty acid amide that activates TRPA1 and inhibits the two-pore potassium channels that normally keep light-touch fibres quiet, which is why it reads as a vibration rather than a flavour. Heat-labile and readily oxidised at those polyunsaturated bonds, so it is a finishing scatter rather than a cooking spice: toast for seconds, grind coarse, add off the heat. Sift out the black seeds if present, they are gritty and carry nothing. Ground huajiao loses the tingle within months.