The filling descends from Chinese dongpo pork, which reached Japan through Nagasaki, the port that kept trading with China during the Edo-period isolation.
A thick slab of pork belly slow-braised in soy sauce, sugar and mirin is folded into a soft steamed bun, sold from bamboo steamers in Nagasaki's Chinatown and eaten on the street.
Takoyaki (Octopus Balls)
Yakitori (Skewered Chicken)
Sapporo Miso Ramen