Nagasaki Shippoku cuisine, mediated through Chinese Dejima trading community; adapted from Chinese dongpo pork via Nagasaki during the Edo period; Okinawan rafute variant developed independently within Ryukyuan kingdom cooking tradition
Buta no kakuni (豚の角煮, 'square-simmered pork') is one of Japan's most celebrated slow-braise preparations: thick-cut pork belly (3–4cm cubes or slabs) braised for 2–3 hours in a combination of soy sauce, sake, mirin, and sugar until the fat becomes translucent and trembling, the collagen fully melted, and the liquid reduced to a lacquered glaze. The dish's origin traces directly to the Nagasaki Shippoku culinary tradition, where Chinese traders brought dongpo pork (东坡肉, named for Song dynasty poet Su Dongpo) to the Dejima trading port. Japan adapted the Chinese preparation to Japanese flavour preferences — less ginger-forward, the sweetness more restrained, the soy balance shifted toward the sweeter nihon-style rather than China's sharper saltier soy. Ryukyu kakuni (Okinawan version, rafute) differs further: it uses awamori (Okinawan distilled spirit) rather than sake and often includes a larger proportion of soy, with the distinct red-brown colour characteristic of Okinawan stewed preparations. The defining technique in proper kakuni is shitani (下煮, pre-cooking): the pork belly must be pre-simmered in plain water (or leek/ginger-scented water) for 30–45 minutes to remove blood, impurities, and excess surface fat before the braising liquid is added — skipping this step produces a greasy, murky, bitter result. The final braised liquid, enriched with rendered pork fat and collagen, should be reduced to approximately half volume and used to glaze the finished pieces. Mustard (karashi) is the traditional accompaniment, its sharpness cutting the fat richness.
Rich, deeply savoury and sweet from soy, mirin, and sugar reduction; unctuous pork fat rendered transparent; layers of soy-sake-mirin caramelisation; karashi mustard cuts the fat and provides the essential sharp contrast — the combination of trembling richness and mustard sharpness is the flavour identity
{"Shitani (pre-simmering in plain water) is mandatory — removes impurities and excess fat before the flavoured braise begins","Fat cap must face down during braising to self-baste the meat layer from below","Final braising liquid reduction to glaze is the flavour concentration step — never discard without first glazing the pork","Low heat throughout: a gentle simmer (bubbles breaking surface slowly) prevents toughening of the muscle fibres","Chinese dongpo pork is the direct ancestor — Nagasaki Shippoku cuisine mediated the tradition into Japanese flavour register"}
{"To test doneness: insert a chopstick through the fat cap; it should pass with only slight resistance and exit cleanly — if it grips, braise for another 30 minutes","Resting overnight in the braising liquid in the refrigerator allows fat to solidify on top for easy removal — the final reheating produces a cleaner, silkier preparation","Adding a small amount of hatcho miso (just 1 tbsp per 500ml liquid) at the beginning deepens the umami without the miso flavour dominating","Okinawan rafute: substitute awamori for sake at 1:1 ratio; add kurozato (Okinawan black sugar) instead of regular sugar — the result is darker, more caramel-forward, and distinctly Ryukyuan","Kakuni bao: steamed bao bun with a slice of kakuni, pickled daikon, and julienned cucumber is the Taiwanese adaptation that has returned to Japanese izakaya menus as kakuni-man"}
{"Skipping shitani — the impurities and excess fat from the initial simmering will cloud and bitter the braising liquid","Using high heat — rapid boiling tightens pork muscle fibres and prevents full collagen melting; patience at low simmer is the technique","Under-braising — kakuni requires a minimum of 2 hours; 3 hours produces the trembling, unctuous fat that defines the dish","Overseasoning the braising liquid before reduction — it concentrates significantly; start lighter than feels necessary"}
Nihon Ryori Taizen — Tsuji Shizuo; Japanese Farm Food — Nancy Singleton Hachisu