Cut the pork belly into 1cm cubes.

Finely chop the shiitake mushrooms and Japanese leek.

In a bowl, combine the pork, shiitake mushrooms, leek, yakiniku sauce, sesame oil, and soy sauce. Mix well to create the filling.

Sift the cake flour and baking powder together in a separate bowl.

Add the sugar to the sifted flour and baking powder.

Gradually add lukewarm water while mixing until a soft dough forms.

Knead the dough well until it reaches the softness of your earlobes.

Divide the dough into 3 equal portions.

Shape each portion into a ball and then roll it out into a circle.

Place 1/3 of the pork filling into the center of each dough circle.

Pinch up the edges of the dough to enclose the filling, creating a bun shape.

Gather the pinched parts to the center, sealing the bun.

Fill a steamer with plenty of water and bring to a boil.

Place the buns in the steamer, ensuring they are not overcrowded.

Cover the steamer lid with a kitchen towel or cloth to prevent water droplets from falling onto the buns.

Steam the buns over high heat for 20 minutes.

Remove the steamed buns from the steamer and let them cool slightly before serving.