Prep the radish: Wash and peel the white radish, then shred it into thin, even strips. Toss the radish shreds with a pinch of salt, mix well, and let sit for 10 minutes to draw out excess water.
Squeeze dry: Wrap the salted radish shreds in a clean cheesecloth (or kitchen towel) and squeeze firmly to remove as much moisture as possible. The drier the radish, the better—this prevents soggy buns later!
Sauté the base: Heat a pan over low heat, add the diced fatty pork, and cook until it renders oil and turns slightly crispy. Add the minced ginger and stir-fry for 30 seconds until fragrant. Add the ground pork, turn up the heat to medium, and stir-fry until the pork changes color. Continue cooking until most of the moisture from the pork evaporates (this keeps the filling tight and flavorful).
Mix & season: Add the squeezed radish shreds to the pan and stir-fry with the pork until well combined. Pour in 1 tbsp light soy sauce, 1 tsp oyster sauce, and 1 tsp white pepper—stir quickly to coat everything evenly. Finally, add 1 tbsp chili powder, chopped green onions, and ½ tsp chicken bouillon. Stir for 30 seconds, then turn off the heat. Let the filling cool completely before using (warm filling will ruin the dough’s rising ability).