Dumplings:

1/2 package round gyoza skins (3 dozen) find them refrigerated, next to the wonton skins in your supermarket

Filling:
1/2 lb. lean ground pork

2 tablespoons finely chopped fresh, peeled ginger root

3 cloves of garlic, finely chopped or crushed

1 green onion, finely chopped white and green parts

1/2 teaspoon salt

1/4 cup dried shiitake mushrooms, soaked and thinly sliced

or 1 tablespoon shiitake powder

1 tablespoon sake or dry sherry or white vermouth

1 tablespoon chicken stock

1 tablespoon soy sauce

1 tablespoon oyster sauce optional

1/2 teaspoon toasted sesame oil

1/2 teaspoon ground white pepper

1 teaspoon cornstarch

Dipping Sauces:

Classic

3 tablespoons soy sauce
3 tablespoons rice vinegar
1 chopped green onion
red pepper flakes (optional)

Sesame Ginger

3 tablespoons soy sauce
1 teaspoon toasted sesame oil
1 teaspoon minced ginger

Spicy

3 tablespoons soy sauce
1 tablespoon rice vinegar
1/2 teaspoon minced garlic
1/2 teaspoon hot chile oil

Feisty!

To shape the dumplings: take one round gyoza skin in the palm of your non-dominant hand.  Dip a finger in the cold water and run it half-way around the inside edge of the circle. This is so that the two edges will stick together when you're ready.

Place a small amount - 1/2 tablespoon is a good amount, although it looks tiny - in the centre of the circle.

Two choices:
a) fold the circle in half and press the edges together, to make a half-moon shape. Be sure to squeeze out any excess air - air pockets can make the dumplings burst when you're cooking them.  This is the classic potsticker shape.

or

b) make the classic "gyoza shape" by pinching together the two sides, folding little pleats into the front half of the skin as you work from one side to the other. Make sure you give a good, firm pinch on the pleats and the end so that they seal nicely, and again make sure you don't get air pockets. Don't try to put in too many pleats - four is plenty. This shape is pretty because it sits up on its bottom, with the pleated "ruffle" at the top.

Place each dumpling on the greased sheet as you finish it. Make sure they're not touching each other. Put the sheet or plate in the freezer until the dumplings are rock-hard - a couple of hours should do it. Then, dump them carefully into a freezer bag and keep in the freezer until needed.

If you want to cook some that day, leave them covered in the fridge.

To cook frozen gyoza:  Steam them in single layer in a bamboo or metal steamer (spritzed with oil) for 10 minutes.  If in doubt, split one open and see if it's still pink. Once steamed, you can serve them as is (with dipping sauce) or you can pop them into an oiled frying pan for a minute or two to crisp up the bottoms.

You can also boil them for about 8 minutes in water or stock - make sure you don't let the water boil too violently, or they may come undone a bit. Pan-fry finish or not, as you like. I sometimes add them to the water that I'm going to use to cook ramen or soba.  Classes the dish right up!

If you want to cook fresh, unfrozen gyoza, this is great: Over medium heat, heat a frying pan with a little oil in it. Add the gyoza, lying on their sides, in a single layer and allow to fry for 2 minutes without touching them (turn the heat down if they're getting to visibly crispy looking). Add a half-cup of water and put a lid on very quickly - leave to continue steaming/cooking for another two minutes. Remove lid and let any water cook away. Gyoza are not usually fried on both sides, just one. It makes a pleasing contrast of textures.  You can, of course, also steam or boil them when they are fresh. Takes a little less time - maybe 6 minutes.