Rehydrate the shiitake mushrooms in the 1 cup warm water for about 15 minutes. Reserve the liquid and chop the mushrooms.
While the mushrooms rehydrate, soak the bean thread noodles in water for about 10 minutes, or until softened. Drain and chop the noodles into 3 to 4-inch long pieces.
While the mushrooms and noodles are soaking, whisk together the oyster sauce, ginger, soy sauce, starch, and black pepper in a small bowl.
Heat the oil in a wok or large saucepan over medium-high heat. Add the shiitake mushrooms, bean thread noodles, carrot, onion, celery, hon-shimeji mushrooms, and green onions and stir fry for about 1 minute. Give the sauce a quick whisk (to re-incorporate the starch) and add it to the pan. Cook, stirring occasionally, until the mixture is heated through and the sauce has thickened, about 3 minutes.
Steam the cabbage leaves for about 3 minutes or until just pliable. Drain and rinse the leaves with cool water. Stuff each leaf with about ⅛ of the mixture.
Hold a cabbage leaf in your hand, open side up. Place ⅛ of the filling mixture towards the stem end, fold in the sides over the mixture, and roll towards the other end. Place the cabbage roll, end roll down, in a bamboo steamer or other steamer. Repeat with the remaining leaves and filling.
Bring the reserved shiitake mushroom liquid to a boil in the wok. Arrange the steamer on top and steam for about 15 minutes. Serve immediately.
Recipe by Go Dairy Free at https://www.godairyfree.org/recipes/chinese-stuffed-cabbage-rolls