Nikuman (Roti Babi Kukus)

Bahan-bahan (20 porsi)

• 2½ cups all-purpose flour (plain flour)
• 2 scant Tbsp sugar
• ½ tsp Diamond Crystal kosher salt
• 1 tsp baking powder
• 1 tsp instant yeast
• 1 Tbsp neutral oil ((plus more for coating the proofing bowl))
• ⅔ -¾ cup water ((start with 160 ml and add more, if needed))
• 2 dried shiitake mushrooms
• ½ cup water
• 1 g reen onion/scallion
• 4 leaves green cabbage ((6.3 oz, 180 g))
• 1 tsp Diamond Crystal kosher salt
• ¾ lb ground pork
• 1½ tsp ginger ((grated, with juice; from 1-inch, 2.5-cm knob))
• 1 tsp sugar
• 1 Tbsp sake
• 1 Tbsp soy sauce
• 1 Tbsp toasted sesame oil
• 1 Tbsp potato starch or cornstarch
• freshly ground black pepper
• soy sauce
• Japanese karashi hot mustard