In a medium pan over medium-high heat, add the lap cheong and pan-fry until crispy and it renders its fat, 5-10 minutes. If there’s no sheen to the pan, add some more oil. Add the shrimp and mushrooms, and stir-fry for another minute. Add the scallions and taro, and stir-fry for 3 minutes. Season with salt, white pepper and sesame oil. Remove from heat and let it cool slightly.

In a large bowl, mix the water and rice flour together until well combined; it should be really thin and watery, like a really watery pancake batter. Now add the taro mixture (no need to wait for it to cool completely). Mix until combined.

Generously oil one 8-inch round cake pan, and pour the mixture into the pan. The mix-ins should be barely submerged; if they aren't, add enough water until the mix-ins are submerged and gently mix the batter to re-combine.

If you have a pressure cooker: place a metal rack in your insert, add enough water to come up halfway up the rack (about 1 cup), and place the taro cake on top of the rack. Cook at high pressure for 15 minutes, then let it naturally release.

If you have a steamer: steam the taro cake in your steamer for 45 minutes. Make sure you start with enough water so the water does not dry out halfway.

If you have neither a pressure cooker nor a steamer, use a wide, moderately deep skillet. Place a metal rack in the skillet, add enough water to come up halfway up the rack, and place the taro cake on top of the rack. Cook over medium heat; depending on how deep your skillet is, this can take 1-2 hours. Add water as needed if you see the pan start to dry out.

The taro cake will be done when a toothpick inserted into the center of the cake comes out clean.

Remove the wu tao gou from the cooking apparatus, and drizzle with the soy sauce and sesame oil. Sprinkle the cilantro and pickled mustard green bulb on top, then scoop and serve hot. You can also let it cool, then slice and pan-fry in a pan with some oil until crispy.