Walk into a Punjabi dhaba in winter and there is often a steel bowl of ginger matchsticks soaking in lemon juice beside the onion rings. Adrak ka achar is the simplest pickle of all: tender ginger, green chilli, salt and lemon, nothing cooked. Young ginger with thin, pinkish skin reacts with the acid and turns a pretty pale pink within a day; older ginger stays yellow but tastes just as good. The flavour is clean, hot and sour, with crunch, and a forkful cuts the richness of sarson ka saag, makki ki roti, chole bhature or a heavy dal makhani. Common mistake: cutting the ginger thick or using fibrous old roots, which stay woody and harsh; slice thin enough to see light through. It is ready when the ginger has softened slightly, the juice tastes less sharp and the slices have taken colour. Fresh ginger in lemon juice keeps in the fridge for up to 2 weeks; discard it if mould appears, the juice turns slimy or the smell turns from fresh-sour to musty. Chef's tip: a pinch of black salt (kala namak) added at the end gives it that dhaba-style sulphurous edge.