
Soak the dried zongzi leaves overnight in plenty of water, keeping them fully submerged with a plate or other weight.
In a separate large bowl, cover the glutinous rice with at least 2 inches of water and soak overnight. The rice will expand as it hydrates.
The next day, soak the meigan cai in cold water for 30 minutes. Lift it out of the bowl, discard the gritty soaking water, and repeat rinsing in fresh water until no sand remains. Squeeze out as much moisture as possible and set aside.
Cut the pork belly into 20 pieces so you have a mix of leaner and fattier pieces for even filling.
Place the pork belly in a pot, cover with water, and bring to a boil. Boil for 1 minute to remove impurities, then drain, rinse, and set aside.
Heat the oil and rock sugar in a wok over low heat until the sugar melts and turns amber. Add the star anise, ginger, and pork belly, then raise the heat to medium-high and lightly brown the pork.
Add the cleaned meigan cai and stir-fry for 1 minute. Stir in the Shaoxing wine, dark soy sauce, light soy sauce, salt, and water.
Bring to a boil, cover, and simmer over medium heat for 20 minutes, stirring every 5 minutes so nothing sticks.
Remove the lid and cook over high heat, stirring constantly, until all the liquid has been absorbed. Discard the ginger and star anise, then transfer the filling to a bowl to cool slightly.
Wipe each soaked leaf clean on both sides, rinse well, and trim about 1/2 inch from the tough base of each leaf. Keep the leaves in fresh water until ready to use so they stay pliable.
Drain the soaked rice. In a large bowl, mix it with sugar, salt, dark soy sauce, and light soy sauce until evenly coated.
Set up an assembly station with the leaves, seasoned rice, pork and meigan cai filling, salted duck egg yolks if using, kitchen twine, and scissors.
To form each zongzi, overlap 2 leaves lengthwise and shape the base into a cone.
Add about half of the rice for one dumpling to the cone. Each zongzi uses about 90 g rice, making about 10 dumplings total.
Place 1 lean piece and 1 fatty piece of pork belly in the center, add some meigan cai, and tuck in 1 salted duck egg yolk if using. Cover with the remaining rice.
Gently compress the filling with one hand while folding the leaves over it with the other. Fold down the excess leaf to create a compact parcel, taking care not to tear the leaves.
Tie each dumpling securely with kitchen twine, but not so tightly that the rice cannot expand during cooking. Repeat with the remaining filling and leaves.
For Instant Pot cooking, pack the zongzi snugly in the pot and add water to cover them by at least 2 inches, staying below the max fill line. Place the steamer rack on top to keep them submerged, cook on high pressure for 70 minutes, and let the pressure release naturally before opening.
For stovetop cooking, arrange the zongzi tightly in a large stockpot and weigh them down with a heatproof plate if needed. Cover completely with cold water, bring to a boil, then reduce to a gentle simmer and cook for 4 to 5 hours. Keep the dumplings submerged at all times, topping up only with boiling water if needed.
Let the cooked zongzi rest for a few minutes before unwrapping. Serve warm.