Prepare the wrappers: dissolve the salt into the hot water. Slowly pour into the flour and mix together with a wooden spoon, or your stand mixer, for 6-8 minutes until a uniform, elastic dough is formed.
Divide dough into two parts, wrap each half in cling wrap and refrigerate for 30 minutes.
Roll out dough on a surface sprinkled with flour or cornstarch. Roll into a thickness of about 1/8-1/16 inch.
With a biscuit cutter, cookie cutter or drinking glass, cut dough into 3 inch rounds. Keep joining the dough scraps, rolling and cutting until it's all used up. Stack the rounds with a bit of flour or cornstarch between the layers.
Prepare the filling: Heat sesame oil in thick bottomed pan or wok. Add the chopped mushrooms and cook for about 1-2 minutes. Add the onions, then the cabbage and carrots, and cook for about 2-3 minutes more.
When the vegetables are softened, add the garlic and ginger, and cook until, fragrant, about 1-2 minutes.
Add the sauces and continue until the vegetables are cooked down. Remove from heat and place in a separate bowl.
Fill and fold the dumplings: Fill each wrapper with about 1 tbsp vegetable filling (don't overfill).
Next, take a small container filled with water, dip your finger in the water, wet the inside edges of the wrapper, fold in half and lightly press to seal.
Pleat the edges with your fingers using this video as a guide.
Cook the dumplings
Steaming: Spray metal steamer with nonstick cooking spray. Place the prepared dumplings inside, making sure they don't touch. Fill a pot with water, but make sure it doesn't reach the bottom of the steamer. Once the water is boiling, place the steamer inside the pot, and cook the dumplings for 10-15 minutes, flipping them halfway through the cooking process. The wrapper should be tender, translucent and noodle-like.
Pan frying: Heat a skillet with about 1 to 2 tablespoons of sesame oil over medium-high heat. Once the pan is hot, place the number of dumplings you want to cook in the pan. Sear them for about 1 to 2 minutes, until the bottoms turn golden brown. Add from 1/4 cup to 1/3 cup of water, immediately cover with a lid, and let the dumplings steam for another 3 to 4 minutes, until the water evaporates.
Make the dipping sauce: Whisk together the soy sauce, rice vinegar and sesame oil in a bowl. Add the garlic and ginger and mix well. Top with chopped green onions and sesame seeds.*
Serve the dumplings with the dipping sauce and enjoy!