Pork and Shiitake Pot Stickers

It never hurts to have a good supply of dumplings on hand. Ours are much tastier and contain much less sodium than the ones you'll find in the store. Plus, they're delivered from the freezer to the plate in just 10 minutes - what could be easier? Just prepare what you need for the evening, and put the rest in the freezer so that you can have something to do later.
Preheat a large skillet over high heat. Pour the oil into the pan; stir to coat. Add 1/2 cup onion, garlic, ginger, and mushrooms; cook, stirring, for 3 minutes. Remove from the pan; cool slightly. Combine the mushroom mixture, 1 tablespoon soy sauce, hoisin sauce, pepper, and pork in a medium bowl.Place 8 gyoza skins on a clean work surface; cover the remaining skins with a damp towel to prevent them from drying out. Place approximately 1 1/2 teaspoons of the pork mixture in the center of each skin. Moisten the edges of the skin with water. Fold in half; press the edges with your fingertips to seal. Place on a baking sheet sprinkled with cornstarch; cover to prevent drying. Repeat the procedure with the remaining gyoza skins and pork mixture.Combine 1/4 cup hot water and brown sugar in a small bowl, stirring until the sugar is dissolved. Add the remaining 1/4 cup spring onions, remaining 1/4 cup soy sauce, vinegar, and sambal, stirring with a whisk until smooth.Preheat a large heavy skillet over high heat. Brush the mold generously with cooking spray. Add 10 stickers to the pan; cook for 30 seconds or until they are lightly browned on one side. Turn the stickers upside down in the pot; carefully add 1/3 cup of water to the pot. Cover tightly; steam for 4 minutes. Repeat the procedure with the remaining pot stickers and add more water, or follow the freezing instructions. After cooking, immediately serve the stickers in pots with dipping sauce.TO FREEZE: Place the dumplings flat on a baking sheet sprinkled with cornstarch for 10 minutes or until they are firm. Place in a large zippered plastic freezer bag with 1 teaspoon cornstarch; toss to combine. Freeze the sauce in a small zippered plastic freezer bag. Freeze for up to 2 months.FOR DEFROSTING: Defrost the sauce in the microwave at high power at intervals of 30 seconds. Stickers in pots do not need to be defrosted.TO REHEAT: follow the cooking instructions, put the frozen dumplings in the pan and increase the steaming time by 2 minutes.