Make the hot water dough: In a stand mixer fitted with a dough hook attachment, combine the flour, salt and two-thirds of the boiling water. Mix on medium speed while slowly adding the remaining water until well mixed and a ball is formed and the dough is not too hot to handle, 3 to 5 minutes. Sprinkle with a little flour if it gets too wet.
On a floured surface, knead the dough until it becomes a smooth, elastic ball. Place back in the bowl and cover with a damp cloth. Allow to rest for at least 1 hour.
Make the dumpling wrappers: Working on a floured surface with floured hands, roll out the dough to form a long 'noodle', 1-inch in diameter. Cut 1/2-inch pieces and turn them over so the cut sides are facing up. Flatten with your palm and roll out thin using a rolling pin. The dumpling wrapper should end up about 3 inches in diameter.
Make the vegetarian filling: Heat the oil in a wok or large saute pan over medium-high heat, then saute the onions and season with a pinch of salt and 1 teaspoon white pepper. Add the ginger and mushrooms and saute 1 to 2 minutes. Add the cabbage, carrots and chives and season to taste. When the mixture is soft, place in a colander to drain. Add the cilantro and sesame oil when mixture is cooled. Check for seasoning.
Make the dumplings: Place a small mound of filling in the middle of the wrapper. (Be very careful not to touch the edges with the filling as this will impede proper sealing of the dumplings. Nothing is worse than dumplings breaking during cooking.) Lightly brush the top half edge with water and fold the wrapper in half to form a half moon shape. Starting on one end fold/pinch the wrapper tightly together. Proceed with this fold/pinch method until the dumpling is completely sealed. There will be approximately 7 to 10 folds per dumpling. Rest the dumplings with the folded edges straight up.
Cook the dumplings: In a nonstick saute pan coated well with 1 tablespoon oil, place the pot stickers flat side down, turn the heat to medium-high and cook until the bottom is browned. Have pan cover ready, add 1/4 inch of water to the bottom of the pan and cover immediately. Be careful, the liquid will splatter! The water will steam the pot stickers. Check them in 5 minutes as more water may be needed. (Ideally, you add about 1/4 inch layer of liquid, depending on the size of the pan.) The trick here is that once the dumplings are firm and fully cooked the water will evaporate and the bottoms will crisp-up again. You can listen to the point no water is left, that is when you can take the lid off.
Make the dim sum dipper: Combining all ingredients in a small bowl and mix well. Serve with the pot stickers.