Take a jug and add 50 ml of water. Stir in 2 ½ tsp of sugar and ¼ tsp of dry yeast, and let it activate for a few minutes until foamy.
In a bowl, sift together 100 g of cake flour and 50 g of bread flour. Add ¼ tsp of salt and ½ tsp of baking powder. Mix the ingredients well until they are even distributed.
After that, Pour the contents of the jug into the bowl, including the foam, and add 25 ml of milk. Mix until a rough dough forms.
Transfer the dough onto a lightly floured surface and knead it until smooth. It should take about 5 minutes.
Return the dough to the bowl and cover it with cling film. Allow it to rest in a warm place until it doubles in size. It takes 40-90 minutes depending on the environment.
For the filling, heat a pan over medium heat and add ½ tbsp of sesame oil. Add the diced onion, boiled bamboo shoots, shiitake mushrooms, wood ear mushrooms, grated ginger, and grated garlic to the pan. Fry them for 1-2 minutes.
Next, add ½ tbsp of soy sauce, 1 tsp of oyster sauce, 1 tsp of miso paste, 1 tsp of black vinegar, ½ tbsp of sake, and 1 tsp of sugar. Also, add 1 tsp of honey, a pinch of salt, a pinch of white pepper, and 1 tsp of Chinese chicken bouillon powder. Mix the ingredients well. Continue cooking until the liquid absorbs and disappears into the mixture.
Prepare a slurry by mixing 1 tbsp of cold water with 1 tsp of potato starch in a small bowl. Turn off the heat and pour the slurry into the pan. Stir the mixture over the residual heat until it becomes glossy and thick.
Transfer the filling to a container and allow it to cool. Once it is cool to the touch, mix in 100 g of ground pork and 1 tsp of lard. Cover the container with plastic wrap and chill it in the fridge until the dough is ready.
Once the dough has doubled in size, gently press out the air and roll it into a cylinder. Cut the dough into equal pieces, each weighing approximately 60g (2oz).
Shape each piece into a round disc shape, cover it with cling film or a clean damp cloth, and let it rest for 15 minutes.
Take the filling out of the fridge. Divide it into portions weighing approximately 60g (2oz) for each wrapper.
Place each ball of dough on a chopping board and flatten it with your palm. Then, use a rolling pin to thin out the edges. The centre should be about 5mm (¼ inch) thick, while the edges should be about 2mm thick.
Roll a part of the filling and place it in the centre of the dough. Bring the top and bottom edges to the middle and pinch them together. Repeat the same process with the left and right edges, and then with each pair of parallel corners. Finally, pinch the middle and twist to close the Nikuman.
Place each completed Nikuman on an individual square of baking paper. Arrange them in the steaming basket. Ensure that there is enough space between each Nikuman and the edges of the basket.
Cover the steaming basket with a lid and let it rest for 15 minutes for the second rise.
After 15 minutes, fill the steamer with cold water and place the steaming basket with the Nikuman on top. Put the steamer on the stove and bring it to a boil over high heat. Once it starts boiling, set a timer for 13 minutes.
Remove the lid from the steamer and enjoy your delicious Nikuman.