In a bowl, combine the cake flour, bread flour, sugar, salt, dry yeast, baking powder, skim milk powder, vegetable oil, and lukewarm water.

Mix the ingredients until they come together.

Knead the dough well until it is smooth.

Form the dough into a ball.

Place the dough in a bowl, cover with plastic wrap, and let it rise for about 40 minutes, or until it has doubled in size (1st rising).

Rehydrate the dried shiitake mushrooms.

Finely chop the rehydrated shiitake mushrooms and onion.

Roughly chop up the cooked bamboo shoots.

In a separate bowl, mix the ground pork, chopped shiitake mushrooms, onion, bamboo shoots, soy sauce, salt, sugar, grated ginger, sesame oil, and katakuriko.

Mix all filling ingredients well to form a cohesive filling.

Once the dough has doubled in size, divide it into 50g portions (10 pieces).

Roll each portion into a ball.

Roll each ball into a 10 cm circle using a rolling pin.

Wrap the filling in each circle of dough.

If the dough doesn't roll out easily, cover it with a kitchen towel and let it rest for 10 minutes.

Once the buns are formed, let them rise again for about 15 minutes at 105F/40C (2nd rising).

Place the buns in a heated steamer.

Cover the steamer with a lid and steam over high heat for 15 minutes.