The Cantonese original (gu lao rou) uses loin pork cut into large chunks, double-fried for a crunchy crust, tossed with a sweet-sour sauce, pineapple, and vegetables. The sauce is rice vinegar, sugar, ketchup, and light soy sauce — the ketchup is traditional in the Cantonese version.
Double-frying
First fry at 160°C sets the batter and cooks the pork through. Second fry at 190°C creates the crunchy outer crust. The crust should be thick enough (batter coating, not a thin dusting) to stay crisp for at least 5 minutes after saucing.
The sauce problem
The most common failure: adding the fried pork to the sauce too far in advance. The crust absorbs sauce rapidly. Serve immediately after tossing — the crunch lasts only 2–3 minutes.