Goishicha (碁石茶)

On a sunny day in midsummer, the mountain town of Otoyo in Kochi Prefecture has an unusual sight. Rows of small, dark squares lie drying on straw mats in the sun, neatly spaced like stones on a go board. They are not stones at all. Instead, each one is a small cake of pressed, fermented tea leaves, and together they give this tea its name: goishicha, or “go-stone tea.” Goishicha (碁石茶) is a post-fermented tea from Otoyo, a mountain town in Kochi Prefecture on Shikoku, the smallest of Japan’s four main islands. Unlike green tea, it is fermented twice: first by mold, then mainly by lactic acid bacteria. That second step gives it a gently sour taste. In this guide, you’ll learn how goishicha is made and where its name comes from. You’ll also see how it nearly disappeared, and how to brew it or cook it into tea porridge at home. The short answer Goishicha is a rare fermented tea from Otoyo, Kochi Prefecture, where farmers have made it for centuries. Makers first ferment steamed tea leaves with mold. Then the leaves ferment again in a weighted barrel, where lactic acid bacteria give them their sour taste. Finally, makers cut the leaves into small squares and dry them in the sun. One piec...