The dish became a fixture of city life for almost the opposite reason you'd expect — as Māori moved into towns after WWII, boil-up thrived because its ingredients, unlike other traditional kai, were the easiest to actually find in a suburban shop.
Pork bones are simmered for hours with potato, kūmara and pumpkin, then loaded with watercress or puha and simple flour dumplings called doughboys, producing a thick, savoury one-pot stew. It's a standard at Rotorua marae gatherings and family kitchens, ladled into big bowls with the bones left in for gnawing.