Finely chop the mushrooms, mince the ginger, and finely chop the scallions, separating the white and green parts.
Heat up 1 tablespoon of oil in a wok over medium heat. Add the finely chopped shiitake mushrooms and let them cook until caramelized, which takes about 4-5 minutes. Be sure not to stir too often and allow the mushrooms to cook undisturbed. Overcooking can cause the mushrooms to turn dry, so keep an eye on them. Once done, set aside and let them cool completely before use.
In a large mixing bowl, combine the ground pork, chopped scallion whites, minced ginger, Shaoxing wine, light soy sauce, dark soy sauce, sugar, sesame oil, and white pepper. Use your hands to whip the filling in one direction for 5 minutes. While whipping, gradually add water, 1 tablespoon at a time, until the filling becomes a thick paste with no standing liquid. Whipping the filling in one direction is an important step that helps to develop the texture of the filling and bind the ingredients together. The addition of water gradually also ensures that the filling is moist but not too wet, which can cause it to fall apart during cooking.
Once the filling is ready, fold in the cooled shiitake mushrooms. Keep stirring for 2 minutes until everything is combined.
To prepare the gluten balls, locate a soft spot and use a chopstick to gently poke a hole without piercing through the other side. Using two chopsticks, slowly rotate and enlarge the hole to approximately 3/8" in diameter, ensuring not to exceed ½". Carefully loosen the inside of the gluten ball with the chopsticks to create ample space for the filling, while maintaining the ball's shape.
Gently fill each gluten ball with the prepared filling, making sure not to break the ball. Repeat until all the balls are stuffed with the filling. This process requires patience!
You may find that you have some filling leftover, but don't worry! The filling inside the gluten balls will have softened and created more space for additional filling. Simply repeat the process of stuffing the gluten balls until all the filling has been used. If you have any leftover filling, you can pack them into meatballs and cook with the fried gluten balls.
In a wok, heat up 1 tablespoon of oil over low heat. Next, add in the sugar, ginger, and scallions, and cook for 1-2 minutes until the sugar has dissolved and the aromatics release their fragrance.
Add the Shaoxing wine, light soy sauce, dark soy sauce, oyster sauce, 1 star anise, and 2 ½ cups water. Bring to a boil, and then reduce the heat to medium.
Place the filled gluten balls in the wok with the openings facing downwards. Cover the wok and let it come to a boil. Then, lower the heat to medium low and let the balls simmer for 10 minutes. Be sure to flip the balls halfway through cooking to ensure they are evenly cooked.
After simmering for 10 minutes, flip the gluten balls so that the openings are facing down once again. Increase the heat and let the sauce reduce until it becomes a thin gravy. You should be left with about 3/4 cup of sauce in the wok. Once the desired consistency is achieved, turn off the heat and serve. Sprinkle the reserved green parts of the scallions over the top as a garnish.