Place sliced taro in a stainless steel colander/steamer and steam on high heat for 30 minutes, until taro is soft and fork-tender.
While taro steams, boil water.
Place the wheat starch into a bowl.
Cook 40g wheat starch by pouring boiling hot water into the wheat starch.
Mix with a pair of chopsticks until all the flour comes together.
Knead with your hands to form a smooth dough. Set aside.
When the taro is done steaming, mash the piping hot taro with a fork or potato ricer right away, until there are no lumps.
Add the cooked wheat starch dough, remaining 30g wheat starch, salt, sugar, 5-spice powder, black pepper, butter, sesame oil and baking ammonia (if using).
Knead until well combined together.
Cover the dough with plastic wrap and let it chill in the fridge for 30 minutes.