1. In a bowl add all the bread dough ingredients. Knead the dough until it becomes elastic and smooth. Lightly coat the bottom of the bowl with oil and place the dough. Cover it with cling film and put it in a warm place for about 1 hour or until the dough doubles in volume.
Prepare the filling
2. Meanwhile, let's prepare the filling. In a skillet, heat 1 tbsp oil and fry the garlic until fragrant. Add leek (or onion) and pork until no longer pink inside.
3. Add the ingredient A and bring to a boil over medium heat. Once the mixture has boiled, turn down heat and simmer for about 20 to 25 min, stirring continually.
4. Turn the heat to high and add dissolved katakuriko/potato starch into the mixture. Thicken the sauce. Let it cool to room temperature.
Put it all together
5. Divide the dough into 10 equal size balls. Lay them across a lightly flour dusted surface. Cover with cling film and let them sit for about 15 mins.
6. Flatten each ball with your hand and roll with rolling pin into about 10 cm in diameter with thin edges. Place the filling in the middle of each of the dough.
7. Wrap and pleat the dough up to seal on the top. Repeat and finish all the buns in this way.
8. Arrange the buns on individually cut baking papers in your steamer. Leave about 3cm space between buns (See pictures). Steam for about 10 mins.