Marinate the julienned pork with the water, light soy sauce, sesame oil, white pepper, vegetable oil, and cornstarch. Allow to sit for 20-30 minutes, while you prepare the rest of the ingredients.
Rinse the rice cakes and drain. If using fresh or frozen rice cakes, you do not have to soak or thaw them. Only soak (according to package instructions) if using dried rice cakes.
Thoroughly wash the baby bok choy (or napa cabbage). Drain, shaking off excess water. If using baby bok choy, separate into individual leaves. If using napa cabbage, cut the large leaves into smaller bite-sized pieces. Also prepare the garlic and scallions.
If using mushrooms, slice them thinly. If using dried shiitake mushrooms, save the soaking liquid.
Place your wok over high heat until it begins to smoke lightly. Add the vegetable oil to coat the wok, and add the pork and garlic. Cook until the pork turns opaque. If using mushrooms, add them now and stir-fry for 1 minute.
Stir in the scallions, bok choy/cabbage, and Shaoxing wine. Stir-fry for 30 seconds, and move everything to the center of the wok to create an even “bed” of vegetables and meat. Distribute the rice cakes on top (this prevents them from sticking to the wok).
Add water (or mushroom soaking water for extra flavor). Depending on how hot your stove gets, you can add 1/2 cup to 3/4 cup. Cover, and cook for 2 minutes to steam the rice cakes and cook the vegetables.
Remove the cover, and add the sesame oil, dark soy sauce, light soy sauce, oyster sauce, white pepper, and sugar. Stir-fry everything together for 1 minute over medium heat. Taste, and season with additional salt if necessary. Continue stir-frying until the rice cakes are coated in sauce, cooked through but still chewy. Plate and serve!