Char siu (叉烧, literally 'fork roast') is the Cantonese barbecue pork preparation — pork marinated in a complex mixture of soy sauce, oyster sauce, hoisin sauce, honey, Shaoxing wine, Chinese five spice, and red colouring, then roasted on a rack or hung in a barbecue oven until caramelized, lacquered, and deeply fragrant. The characteristic deep red-mahogany colour (traditionally from red fermented bean curd, hong doufu ru, now often from red food colouring) and the sweet, sticky glaze of the maltose are the defining visual and flavour signatures. Char siu is the most widely eaten of all the siu mei preparations and appears in or with dozens of other preparations: char siu bao (stuffed buns), char siu so (flaky pastry), char siu cheung fun (rice noodle rolls), and noodle soups.
The marinade: Per 500g pork shoulder (the best cut — pork butt with fat marbling): 3 tbsp light soy, 1 tbsp dark soy, 2 tbsp oyster sauce, 2 tbsp hoisin sauce, 2 tbsp honey, 1 tbsp Shaoxing wine, 1 tsp Chinese five spice, 2 tbsp rock sugar or white sugar, 1 tbsp red fermented bean curd (nan ru) — optional but traditional for depth of flavour and colour. Marinate 4-8 hours minimum; overnight is ideal. The glaze: 2 tbsp maltose (mai ya tang) mixed with 1 tbsp honey and 1 tbsp warm water — applied in the final 10-15 minutes of cooking for the characteristic sticky, glossy surface. Roasting: Preheat oven to 220C. Place pork on a rack over a foil-lined tray. Roast 25 minutes. Flip. Roast a further 15 minutes. Apply the maltose glaze. Return to oven 5 minutes. Apply a final glaze. Rest 5 minutes before slicing.
Eileen Yin-Fei Lo, Mastering the Art of Chinese Cooking (2009); Fuchsia Dunlop, Land of Fish and Rice (2016)