Mix pork, onion, water chestnuts, soy sauce, ginger (optional), garlic, sesame oil.
Season with pepper.
Place a spoonful of this mixture towards the center of one half moon/triangle of a wrapper.
Use water to slightly moisten the semi-circular or triangular edge of the half of the wrapper you have just filled.
Fold the empty half of the wrapper over and crimp or pleat the edges lightly to seal.
Stand the dumplings up so that they look like little old-ladies' purses.
Freeze extras in batches of 16 or 20. Cook the rest.
Heat a bit of oil in a large pan (or a few pans).
Fry the dumplings for 1-3 minutes until golden brown on the bottom.
Add 1/3-1/2 cup of water to the pan, cover, and cook at medium heat for 3-5 minutes.
Remove the lid and simmer low for 1-2 more minutes.
Drain or dry on a rack or towel if so desired.
Combine all ingredients for the Dipping Sauce and serve in a bowl beside the postickers.