Combine all filling ingredients in a large mixing bowl and mix thoroughly. Cover and refrigerate until ready to use, up to a day but preferably within an hour or two.
In the medium bowl mix flour with ¼ cup of water and stir until water is absorbed. Continue adding water one teaspoon at a time and mixing thoroughly until dough pulls away from sides of bowl. We want a firm dough that is barely sticky to the touch. (Food Processor Method: Place the flour in the work bowl of a food processor with the dough blade. Run the processor and pour the warm water in until incorporated. Pour the contents into a sturdy bowl or onto a work surface and knead until uniform and smooth. The dough should be firm and silky to the touch and not sticky.) Note: it’s better to have a moist dough and have to incorporate more flour than to have a dry and pilling dough and have to incorporate more water.
Knead the dough about twenty strokes then cover with a damp towel for 15 minutes.
SHAPE THE DUMPLINGS
Take the dough and form a flattened dome. Cut into strips about 1-½ to 2 inches (4 to 5 cm) wide. Shape the strips into rounded long cylinders. On a floured surface, cut the strips into ¾ inch (2 cm) pieces. Press palm down on each piece to form a flat circle (you can shape the corners in with your fingers). With a rolling pin, roll out a circular wrapper from each flat disc, about 1/16th inch (2 to 3 mm). Take care not to roll out too thin or the dumplings will break during cooking. Leave the centers slightly thicker than the edges.
Place a tablespoon of filling in the center of each wrapper and fold the dough in half, pleating the edges along one side (see images in Jen’s post for how to fold pleats). Place the shaped dumplings on the floured plate. Keep all unused dough under damp cloth.
COOK (CHOOSE ANY OF THE FOLLOWING METHODS)
BOIL: Bring a large pot of water to a boil and add dumplings to pot. Boil the dumplings until they float.
STEAM: Place dumplings on a single layer of napa cabbage leaves or on a well-greased surface in a steamer basket with lid. Steam covered for about 6 minutes.
PAN FRY (potstickers): Place dumplings in a frying pan with 2-3 tablespoons of vegetable oil. Heat on high and fry for a few minutes until bottoms are golden. Add ½ cup (120 ml) water and cover. Cook until the water has boiled away and then uncover and reduce heat to medium or medium low. Let the dumplings cook for another 2 minutes then remove from heat and serve.
Combine all ingredients in a small bowl, amounts of optional ingredients to taste.