Spoon out the oil from the wok, leaving about 2 tablespoons behind. Melt the rock sugar in the oil over low heat. Add the ginger, garlic, and scallion whites, and let it cook for 1-2 minutes. Turn the heat up to medium high and immediately add the duck pieces, spreading them out in a single layer. Cook the duck for about 2 minutes on each side and add the Shaoxing wine, oyster sauce, light soy sauce (and the fermented bean curd sauce if you decide to use it), dark soy sauce, and water. Stir ever