Make filling: Combine the zucchini matchsticks and ½ teaspoon salt in a bowl. Mix well and let it sit for 5 to 10 minutes.

Combine the chicken, onion, garlic, 1 teaspoon salt, ground black pepper, milk, and potato starch in the food processor. Blend 1 minute until smooth and well mixed. Put the filling into a bowl.

When the zucchini is withered and wet, gently squeeze out the excess water with both hands and add it to the filling in the bowl.

Add the sesame oil to the filling and mix well with a spoon.

Shape dumplings: Set out a small bowl of water. Lay a dumpling skin flat on your palm. Dip your index finger in the water and wet the edges of the skin so that it will seal easily.

Spoon a heaping tablespoon of the filling into the center and fold the skin over the filling. Press the edges to seal, and make 8 to 10 small pleats to give the dumpling a pretty appearance and seal it more tightly.

Place it on a plastic-lined platter. Repeat with the remaining filling and dumpling skins. You will make about 28-30 dumplings.

Freeze dumplings: Place the dumplings on a large platter lined with plastic wrap. There should be a little gap between the dumplings so that they don’t stick to each other. Freeze for several hours or overnight, until frozen solid.

Place each dumpling into a plastic bag or container, and then put them back to the freezer. You can freeze them for up to 3 months.

Steam dumplings: Bring some water to a boil in a steamer. Line the steamer basket with parchment paper or lettuce leaves. Add some dumplings and cover. Steam for 10 minutes over medium high heat. Remove from the heat.

Serve, or use in dosirak: Take the dumplings out of the steamer and serve with the seasoning sauce. If you’re making a dosirak, let them cool for a few minutes before packing them in with the other items in the lunch box. Be sure to accompany with the seasoning sauce.

Seasoning sauce: Combine 1 tablespoon soy sauce, 2 teaspoons white vinegar (or apple cider vinegar), a pinch of gochu-garu (Korean hot pepper flakes) and mix well and transfer it to a small bowl or pack it with a dosirak by putting it in a small container and covering it tightly.