Chashu is slowly braised pork belly, a staple Japanese dish infused with traditional flavors of soy sauce and sake. The dish can be made with flat pork belly, but the pieces can also be rolled to create more sophisticated versions which cook more evenly.
Prepared pork belly is covered in a fragrant mixture of soy sauce, mirin, sake, and sugar. The liquid is additionally seasoned with sliced ginger and scallions, and the meat is braised on low heat for hours, until it soaks up all the layered flavors and turns the thick pork belly into an incredibly soft, tender, and juicy piece of meat.
If the skin is left on the meat, it will caramelize during braising, becoming slightly gelatinous and affecting the final texture of the dish. The name and origin of this Japanese classic probably stems from char siu, the popular Chinese roasted pork dish.