Char siu is Cantonese red-roasted pork: strips of pork shoulder or belly marinated in a mixture of soy sauce, oyster sauce, hoisin sauce, Shaoxing wine, five-spice, and honey, then roasted at high heat with repeated glazing during the cook.
The red colour
The deep red comes from red fermented tofu (nam yu) or red yeast rice in traditional recipes. Modern commercial versions use red food colouring. Neither affects flavour significantly. The caramelised glaze is the primary quality marker.
Applications
Char siu is eaten directly as roast pork, sliced over rice (char siu fan), used as the filling for char siu bao (roast pork buns), and scattered over noodle soups. The fat-to-lean ratio of pork shoulder produces the most flavourful result; pork fillet is drier.