In winter, when the fat, fleshy red chillies of Banaras and Rajasthan come to market, families in Varanasi, Lucknow and Jaipur set aside a day to make bharwa lal mirch. The chillies are large and only mildly hot, more like a long pepper, so they are emptied, packed with a sharp masala of coarse yellow mustard, fennel, fenugreek, nigella and amchur (dried mango powder), and cured under smoked mustard oil in the sun. After a week the skins soften and the filling turns tangy and pungent, almost a meal in itself; one chilli sliced beside dal-chawal, puri-sabzi or a plain paratha is plenty. Wear gloves for the cutting, and make sure the chillies are fresh, glossy and firm. Common mistake: stuffing chillies that are still damp inside after washing; dry them for a few hours, cut side down, or the jar will spoil. Keep them under oil, use only a dry spoon or tongs and discard if mould appears. Chef's tip: a spoon of lemon juice in the filling helps it cling and gives a brighter tang.