Shikarpur, the old trading town in upper Sindh, is famous across Pakistan for one thing in a jar: a dark, oily mixed pickle that families say keeps for a year. It is made in May and June when green mangoes are sour and limes are cheap, cured in the hot Sindhi sun, and eaten all year with daal chawal, aloo paratha at breakfast, Sindhi biryani and plain roti with yoghurt. The flavour is sour, salty and fiery, with the bittersweet crunch of fenugreek, anise-sweet fennel and the onion note of kalonji, all carried in pungent mustard oil; the mango stays firm, the lime rind turns soft and chewy and the chickpeas stay nutty. Its long life comes from salt, sour fruit, vinegar and a thick layer of oil, so keep every piece under the oil. Common mistake: any water at all — wet fruit, a damp jar or a wet spoon — which brings mould within days. Dry everything in the sun or a low oven. It is ready after 2–3 weeks, when the lime skins are tender and the oil has turned red and fragrant. Chef's tip: heat the mustard oil until it just smokes and let it cool; this softens its raw bite.