Combine ground pork, shrimp, ginger, light soy sauce, Shaoxing wine, salt, and white pepper in a large bowl. Stir with a spatula until the ingredients are well combined and form a sticky paste. Thorough mixing is essential here, so your dumpling filling will stay together when you wrap dumplings. Cover with a plastic wrapper and allow to marinate in fridge until you’re ready to wrap the dumplings.
Cut 6 to 8 pieces napa cabbage leaves (just enough to line the steamer) and keep for later. Cut the rest of the cabbage into small cubes and set aside.
Sprinkle 2 pinches of salt onto the cabbage and mix well with your hands. Allow this to sit for 10 to 15 minutes. Use a few layers of cheesecloth or paper towel to squeeze out extra water.
Just before wrapping dumplings, add the napa cabbage, green onion, and sesame oil into the pork mixture. Stir to mix well.
Work on the dumplings one by one. You can watch this video if you're using frozen dumpling wrappers. Or watch this video if you're using homemade dumpling wrappers.
Scoop about 1 to 2 tablespoons (depends on the size of dumpling wrapper you use) of dumpling filling and place it in the center of the wrapper. If you’re using pre-made dumpling wrappers, dip your finger into a small bowl of water and wet the outer edge of the dumpling wrapper. Fold both sides into a half-moon shape and pinch the middle points together. Hold the dumpling with one hand and start sealing the edges into pleats with the other hand. Once you have sealed the dumpling, firmly press the pleated side with your fingers to make sure the dumpling is well sealed. If you put in too much filling and have trouble sealing the dumpling, remove extra filling and fold the dumpling again.
If you plan to cook the dumplings immediately, place dumplings onto a well-floured cutting board about a finger width apart.
If you plan to freeze the dumplings, line a baking sheet with aluminum foil and place dumplings on top.
Line the bamboo steamers with napa cabbage leaves. Place dumplings into the steamer a finger width apart. Add two inches of water into a wok or a large pan that can comfortably fit your steamer. Place the steamer into the wok making sure the water doesn’t touch the dumplings when it begins to boil. Cover the steamer and cook over high heat for 10 minutes.
Store the wrapped, uncooked dumplings in the freezer for up to 1 month. To freeze properly, seal the baking sheet tight with plastic wrapper and allow the dumplings to freeze completely. To save freezer space, transfer the frozen dumplings into large containers or a gallon bag. Be careful not break them when you stack the dumplings and do not place other things on top of your dumplings bag.
To cook the frozen dumplings, steam directly from the freezer without thawing. It takes about 15 to 20 minutes to cook through.