Bonito flakes — katsuobushi (鰹節) in Japanese — are gossamer, pinkish-brown shavings planed from a block of skipjack tuna that has been simmered, smoked over weeks and fermented with a noble mould until it is as hard and dry as a piece of wood. Intensely smoky, deeply savoury and almost meaty, the flakes are one of the two pillars of Japanese cooking: steeped with kombu kelp they make dashi, the clear, umami-rich stock beneath miso soup, simmered dishes and noodle broths, because the inosinate in the fish and the glutamate in the kelp amplify each other. Strewn over hot okonomiyaki, takoyaki or chilled tofu, the feather-light flakes appear to writhe and "dance" in the rising heat.