Roast pork (char siu)
Pork belly, tied into a roll and slowly braised in soy sauce, mirin, sake and sugar, then thinly sliced: tender, salty-sweet, with a soft rim of fat.
Chashu is the Japanese take on Cantonese char siu, yet clearly different from it: rather than being glazed and roasted in the oven, pork belly, or less often shoulder, is rolled, tied and braised for hours in a sweet and salty liquid of soy sauce, mirin, sake and sugar. The meat becomes so soft it almost parts with chopsticks, and the fat nearly melts on the tongue. The slices go cold or lukewarm onto ramen, rice or into bento, often seared or torched just before serving so the edge caramelises. Ready-sliced chashu sometimes turns up vacuum-packed or frozen in Asian grocery shops, but most people make it themselves from pork belly bought at a butcher. The leftover braising liquid is usually kept, for marinating eggs or seasoning the soup.
Substitute:
Cantonese char siu from an Asian grocery or a Chinese barbecue shop can stand in, but it is roasted rather than braised, firmer, sweeter, coloured red and seasoned differently, often with five-spice powder. You only get close to the original by slowly braising pork belly yourself in soy sauce, mirin and sugar.