Japan (Edo-period Tokyo — Nihonbashi fish market area; shitamachi working-class cuisine tradition)
Negima nabe (葱鮪鍋, 'leek-tuna hotpot') is an Edo-period Tokyo hotpot tradition that originated as working-class fishmonger and riverside market cuisine — a practical use of fatty tuna trimmings (parts considered low-grade by sushi standards but prized for their rich fat content in simmered preparations) combined with negi (long green onions/leeks). The dish exemplifies Edo pragmatism: parts of the fish too oily for raw consumption (toro belly, collar, dark flesh near the spine) that would otherwise be discarded or sold cheaply were combined with the sweetness of deeply simmered negi to create a winter hotpot of extraordinary depth. The broth is typically a strong dashi with soy and sake; the negi are added first and cooked until completely softened to sweetness, then the fatty tuna pieces are added briefly — just enough to set but not fully cooked through, retaining a pink centre. The fat from the tuna disperses into the broth, enriching it further. Premium versions at traditional Tokyo negima nabe restaurants use hon-maguro (Pacific bluefin) trimmings, and the long simmered negi softened to near-dissolving is as essential as the fish. The dish is closely associated with the culture of Tokyo shitamachi (low city) merchant neighbourhoods.
Rich, fatty tuna dissolving in strong soy-dashi; sweet soft leeks as counterweight; warming, robust, deeply umami Edo winter hotpot
{"Fatty tuna trimmings (collar, belly, dark meat) preferred — richness is the point of this preparation","Negi (Tokyo negi / Shimonita negi) cooked first until nearly dissolved — sweetness is essential counterweight","Brief cooking of tuna: add pieces and simmer 2–3 minutes only — overcooking destroys the fatty richness","Strong soy-dashi broth absorbs and is enriched by tuna fat released during brief simmering","Edo shitamachi tradition: working-class pragmatic use of fishmonger's trimmings"}
{"Shimonita negi (a specific long leek from Gunma) is the traditional choice — sweeter and more substantive than standard negi","Add a piece of konbu to the broth from the start for cleaner, deeper dashi base","Tuna collar (kama) is the supreme cut for this dish — maximum fat, extraordinary flavour when just-cooked","End the meal by adding udon noodles to the tuna-enriched broth — one of the great締めshime (finishing) preparations"}
{"Using lean tuna loin — defeats the purpose; needs the fatty collar and belly trimmings","Over-cooking tuna pieces — brief simmer only; grey all the way through is overcooked","Not pre-cooking negi until soft — adding raw leeks simultaneously with fish results in undercooked negi","Under-seasoning the broth — Edo-style cooking uses strong soy presence for robust flavour"}
Japanese Cooking: A Simple Art — Shizuo Tsuji; Edo no Ryori (Edo Cuisine) — Various Japanese sources