Teriyaki sauceeel sauce, or soy sauce (for dipping)
In a medium mixing bowl, use your hands the evenly combine the pork, water chestnuts, green onion, soy sauce, rice vinegar, sugar, ginger, cornstarch, salt, and pepper.
Use a 2-inch circular cookie cutter to cut each wonton wrapper into a circle. (If you want to skip this step, fold your wontons into a triangle instead of a half circle in step #4.)
Scoop 1 to 1 1/2 teaspoons of the pork mixture onto the wonton circles (placing the filling to one side of the wonton, not in the center).
Dip your finger tip in some water and run it around the edge of one wonton to moisten it. Fold the wonton edges together, over the filling, to create a half circle. Use your finger tips to seal the edges together. Repeat with the remaining wonton wrappers and filling - working with one dumpling at a time.
Bring about 2-inches of water to a roaring simmer in a large pot. Place a vegetable steamer in the bottom of the pot, making sure the water is just below the bottom of the steamer.
Place the dumplings side-by-side in the steamer, but not overlapping. Cover the pot and cook for 10 minutes.
Uncover the pot and remove the dumplings to a serving plate. Repeat with remaining dumplings.
Sprinkle the cooked dumplings with green onion and serve with your favorite dipping sauce.
I definitely recommend doubling this recipe! I cook half the day we make them, and then put the rest on a baking sheet in the freezer. Once frozen, the dumplings are transferred to a ziploc bag for storage. I usually fry the dumplings that are frozen (in hot oil until golden brown - about 3-4 minutes), but if you want to steam them - place as many dumplings as you want on a plate and thaw them in the fridge before steaming.