Cu liu yu (醋熘鱼, vinegar-braised fish) is a classic Shandong preparation of whole fish (traditionally yellow river carp, li ji yu, 鲤鱼) braised in a sweet-vinegar sauce — a dish that exemplifies the Shandong culinary preference for combining vinegar with a rich, savoury-sweet sauce to complement freshwater fish. The Hangzhou version of this dish (West Lake Fish, xi hu cu yu, 西湖醋鱼) is its close relative. In Shandong, the sauce tends to be richer and more assertively vinegared than the Jiangnan version.
The fish: Score the fish on both sides in a crosshatch pattern, cutting to the bone — this allows the fish to cook through quickly and the sauce to penetrate. Dust with cornstarch. Pan-fry in hot oil until golden on both sides, then remove. The sauce: Fry scallion, ginger, garlic in the same oil. Add Shaoxing wine. Add 200ml superior stock, 3 tbsp Chinkiang vinegar (Zhenjiang vinegar — the specific vinegar of Jiangsu, dark and mellow), 2 tbsp sugar, 1 tbsp light soy, 1 tsp dark soy. Return the fish to the pan. Braise in the sauce at a moderate simmer for 8-10 minutes. The fish should be fully cooked — the flesh should flake when pressed gently at the thickest point. Remove the fish to a platter. Reduce the braising liquid until thick and glossy. Thicken further with a cornstarch slurry if needed. Pour over the fish.
Fuchsia Dunlop, Invitation to a Banquet (2023); Ken Hom, Complete Chinese Cookbook (2011)