Buckwheat is the triangular, three-cornered seed of a fast-growing broadleaf herb, eaten and milled like a grain but botanically a pseudocereal — kin to rhubarb, sorrel and dock, not to wheat or any true cereal, and entirely free of gluten. Earthy, nutty and robustly savoury, the hulled groats are simmered as porridge or, toasted first, as Russian and Ukrainian kasha, while the dark, speckled flour is the soul of Japanese soba noodles, Breton buckwheat galettes and the yeasted blini of Eastern Europe.