On summer days in Bishkek and Osh, blue and yellow street barrels sell maksym by the glass, next to chalap and kymyz. It is a sour grain drink of Kyrgyz herders: barley (or millet or corn) is toasted, ground and cooked with fried wheat flour into a thin gruel, then left overnight with a little of yesterday's batch until it turns pleasantly sour and slightly sparkling. It is drunk cold with plov, samsa or simply to cool down in July heat. It tastes nutty, like toast and rye bread, with a yogurt-like tang and a gentle salty edge; the texture is thicker than kvass, about like thin buttermilk. Like all ferments it develops a trace of alcohol, well under 1% when drunk young. The classic mistake is adding the starter while the gruel is still hot, which kills it; wait until it feels just warm, about 30 °C. It is ready when small bubbles rise, it smells pleasantly sour and a foamy cap forms. Keep it in the fridge in a loosely capped jug for 3–4 days; it gets sourer and more alcoholic as it sits. Discard if you see coloured mould, slime or smell anything rotten. Contains gluten. Chef's tip: toast the barley until it smells like coffee for the deepest flavour.