For two and a quarter centuries, Japan was effectively blocked off from the outside world. The only point of ingress or egress: the trading port of Nagasaki. That made this western city a crossroads of culture and of cuisine. These diminutive sandwiches – a slab of stewed pork belly in hearty gravy with a few spinach leaves between the sort of spongy, springy, steamed white bun used in Peking duck – are one of the city’s signature tastes.
