Japan (yoshoku evolution, 1913 attributed to Rengatei restaurant in Ginza Tokyo; now a nationwide staple from convenience stores to specialist donburi restaurants)
Katsudon (カツ丼, 'cutlet rice bowl') is a donburi bowl of white rice topped with a tonkatsu pork cutlet that has been simmered briefly in a sweet-savoury dashi-soy-mirin broth and then enveloped in a barely-set, softly scrambled egg before being poured over the rice. The dish is one of Japan's most beloved comfort foods — the twice-cooked cutlet (fried, then gently simmered in broth) and the silky, partially set egg together produce a dish greater than the sum of its parts. The katsu simmering liquid — dashi, soy, mirin, and sometimes sugar in a small shallow pan — must be strongly seasoned but not overpowering: it must flavour both the cutlet and the egg without making either too salty. The egg is beaten with chopsticks (not uniformly — loose strands are better than completely beaten) and poured around and over the cutlet in the simmering broth; the heat of the broth sets the egg to a barely-cooked, custard-soft state before the whole assembly is lifted with a lid and slid over the rice. The defining quality of great katsudon is the egg texture: it should be molten, barely set, yielding — never fully cooked or rubbery.
Sweet-savoury dashi-soy broth soaking into cutlet and rice; silky barely-set egg; crispy (now softened) panko crust; the combination is greater than its parts — the definition of Japanese comfort food
{"Twice-cooked cutlet: fry then simmer in broth — the two-stage technique transforms the cutlet's character","Loosely beaten egg: chopstick-beaten to maintain streaks rather than uniformly mixed — creates texture variation","Egg set-off-heat: the residual heat of the broth finishes the egg; must be served before over-setting","Dashi-soy-mirin broth balance: strongly flavoured to penetrate the thick cutlet; balanced to not overwhelm the egg","Donburi assembly: broth-soaked cutlet and egg slid as one piece over rice; the broth seasons the rice too"}
{"Individual oyako nabe (small shallow pans) are essential for properly controlled egg setting — not a shared pan","Slide the lid slightly before lifting — a small steam vent slows the egg setting slightly for more control","The broth should have about 3 tbsp per portion: enough to season the cutlet and partially cook the egg","Onion simmered in the broth before adding the cutlet becomes sweet and soft, adding depth to the bowl"}
{"Over-cooking the egg — the most common failure; katsudon must be served immediately when egg is barely set","Beaten egg too uniformly — lose the streaky, textured egg quality; loose beating preserves it","Wrong simmering time for the cutlet — 1–2 minutes only; too long produces a soggy, oil-soaked cutlet","Not serving immediately — the egg continues setting from residual heat; delay ruins the texture"}
Richie Donald, A Taste of Japan