Ker is a leafless desert shrub that grows wild across Kutch and the Thar, and in April and May, before the monsoon, it is covered in small green berries that families pick by hand. Fresh ker are fiercely bitter, so they are soaked and boiled until the bitterness fades, then pickled with split mustard, split fenugreek, chilli and lemon juice and covered in oil. The berries are firm, pea-sized and slightly chewy, with a sour, earthy, caper-like flavour under the mustard heat. In Kutch the pickle goes with bajra rotlo and buttermilk, or is mixed into khichdi; across Rajasthan the same berries go into ker sangri. The common mistake is rushing the soaking: if the water is not changed several times the pickle stays harsh. Taste a berry: it should be pleasantly sour-bitter, like an olive, not acrid. It is ready to eat after 3–4 days, once the berries have absorbed the lemon. Boiled ker are low in acid, so the lemon matters and the pickle lives in the fridge, where it keeps up to 2 months. Abroad, use dried ker from Indian grocers (they swell back well), or, at a pinch, capers soaked to remove the salt. Chef's tip: add a few cubes of raw mango in season for extra sourness.