Chop the rehydrated shiitake mushrooms. Chop and boil the bamboo shoots. Boil the cabbage until tender and chop it up. Squeeze out the water. Mince the leek, ginger, and garlic.
Mix [4] together. Sprinkle the potato starch and mix well.
Combine [3] and [5], and mix them well until the mixture becomes sticky. Divide the mixture into 12 equal parts and shape them into balls.
Sift [A] together into a large bowl.
Combine [B] in a separate bowl, dissolve the seasonings, and add hot water.
Add [2] to [1] and mix well using cooking chopsticks. When the dough holds together, cover it with a damp cloth and let it sit for 30 minutes.
Take [3] out onto a surface sprinkled with flour and lightly knead it to make it smooth. Stretch the dough into a bar and cut it into 12 pieces.
Roll each of [4] into balls. Spread each ball into a flat circular shape and place the meat filling in the center. Roll it back into a bun.
Place the buns in a heated steamer and steam them over high heat for 15 minutes.
