For the dough: Combine the flour and salt in a large heatsafe bowl. Slowly pour in the boiling water while stirring, until you have a coarse meal mixture. Stir in 1/2 cup cold water to form a dough.
Knead the dough on a lightly floured surface for 10 minutes, adding more flour as necessary, until the dough is smooth and slightly sticky. Cover the dough with a damp towel and let sit for 20 minutes.
For the filling: In a large bowl, combine the ground chicken, chicken broth, sugar, soy sauce, vinegar, ginger, salt, scallions and a bunch of turns of pepper.
To assemble the dumplings, divide the dough into 24 balls. Roll them out into 4-inch circles, flouring the surface as needed. Place 1 tablespoon filling in the center of each and fold in half to make a half-moon shape, pleating the edges to seal well.
Bring a large pot of water to a boil. Heat a thin layer of oil in a large skillet over medium-high heat. Boil the dumplings in batches for 4 minutes. Remove them with a slotted spoon, allowing excess water to drip off, then transfer to the hot oil (be careful because this step can get spitty). Cook until the dumplings are browned, 2 to 3 minutes. Transfer to a plate lined with a paper towel and let cool slightly. Alternatively, to steam the dumplings, line a bamboo steamer with blanched cabbage and steam over boiling water until the filling is cooked through, 10 to 15 minutes.
For the dipping sauce: In a small bowl, combine the soy sauce, vinegar, sesame oil, scallion and red pepper.