Heat the vegetable oil in a wok over medium heat until about 300 degrees F. Fry the fish until slightly brown. Drain thoroughly and set aside. If carp is not available perch can be substituted.

Remove all but 2 tablespoons of the vegetable oil from the wok. Turn the heat to high and add the scallion, garlic and ginger. Stir-fry for about one minute. Add the cassia bark, star anise and continue to stir-fry for another 30 seconds. Add the cooking wine, soy sauce, Chinese black vinegar, salt, sugar and water. Bring the liquid to a boil.

Turn the heat down to low and line the bottom of the wok with two layers of large napa cabbage leaves. Then arrange the fried fish side by side on top of the napa cabbage. Simmer the fish on very low heat for about five hours. Check the liquid level every 30 minutes and add water as needed to keep the fish submerged.

After five hours turn the heat up until the liquid has reduced and just covers the napa cabbage. Turn the heat off. Gently remove the fish from the wok and arrange them neatly in a covered container. Remove the napa cabbage from the wok and discard. Pour the reduced bracing liquid and the sesame oil over the fish. Refrigerate covered overnight.

Serve the whole fish cold on a plate garnished with scallions. Pour a little of the braising liquid over the fish.