Warm the oil in a skillet and cook the onion with a pinch of salt until softened. Add the cabbage with another pinch of salt and cook until tender. Stir in the garlic and ginger until fragrant, then let the mixture cool completely before moving on.

Add the ground chicken, bamboo shoots, sugar, bouillon powder, white pepper, a bit of tapioca starch, salt, and sesame oil into the bowl with your cooled vegetables. Use your hands to mix everything together until it's fully combined, then chill it while you make the dough.

Sift your wheat starch and tapioca starch together into a large bowl. Dissolve salt into boiling water, then slowly pour it over the starch while stirring with a wooden spoon or chopsticks. Cover and let it rest for a few minutes before kneading in the oil.

Turn the rested dough onto a lightly dusted surface and divide it into portions. Roll each portion into a log, then cut it into equal pieces and shape each one into a smooth little ball. Keep the balls covered with a damp towel so they don't dry out.

Working with one dough ball at a time, press it flat and roll it into a thin circle with your rolling pin. Place a small spoonful of chicken filling in the center, then gently lift the dough and fold it over to create a half-moon shape.

Tuck the open edges of the dough inward so they meet, then press the dumpling down gently to flatten the bottom into a long sheet. Trim the edge into a wavy pattern like a ghost's blanket, then press two black sesame seeds on top for the eyes.

Arrange the dumplings in your steamer basket with space between each one, then steam over boiling water until the filling is cooked through and the wrapper turns translucent. Let them cool for a minute before serving warm.