In a medium mixing bowl, prepare the potsticker filling by combining the pork, cabbage, garlic, ginger, onion, mushrooms, sesame oil, and San-J Tamari Soy Sauce until just combined. If the mixture does not adhere, add the optional beaten egg as a binder.
To stuff the potsticker wrappers, dip your index finger into the warm water and moisten the entire outer edge of one potsticker wrapper. Scoop 1 teaspoon of the filling and place in the center of the wrapper. Fold over the wrapper to create a pouch and crimp the edges shut with your fingers. Place on a baking sheet and cover with a damp dishtowel. This prevents the potstickers from becoming dry. You may sprinkle the cookie sheet with a little cornstarch to keep the potstickers from sticking to each other. Continue stuffing and crimping until you have prepared at least 80 potstickers. (Note: At this point, you may freeze any remaining filling for future use.)
In a large sauté pan, heat 2 tablespoons of vegetable oil to medium heat. Cook the potstickers in batches, 6 at a time, without crowding the pan. Brown one side of the potstickers and add 1 to 2 tablespoons of water. Quickly cover the sauté pan with an airtight lid to steam the potstickers. As soon as the water has evaporated, remove the potstickers to a warmed serving platter. Keep warm as you repeat the cooking process with the remaining potstickers.
To prepare the dipping sauce, combine the San-J Tamari Soy Sauce, lime or lemon juice, sesame oil and red pepper flakes in a small bowl. Whisk thoroughly and let stand for several minutes to allow the flavors to marry. Serve the potstickers with the sauce.