Half an hour before you want to serve the dumplings, bring a large pot of water to a boil over high heat and add 2 tablespoons salt. Cover and keep at a simmer while you prepare the dumplings.
Flour your work surface and turn the dough out. Cut it into 4 pieces. Flatten and stretch one piece of dough, or use a rolling pin to roll it out; you want a thin oval about 10 inches long.
Use the rim of a jar or bowl that is about 4 inches in diameter as a guide and cut out circles with a knife, cutting them close together. Pull the scraps together, roll out again, and cut out another circle or two.
Fill the first circles: Place a generous tablespoon of filling in the center of one circle. Pull up a bit of the edge and then another bit next to it, pleating the second one over the first, and continue around the circle until you have created a pillow with a gathered top. Pinch the top 1/2 inch below the top edges of the dough and twist to seal the topknot well. Set aside on a well-floured surface.
Repeat to fill the remaining rolled-out circles of dough. (If your kitchen is very dry, cover the shaped dumplings loosely with plastic wrap or a slightly damp cloth.) Then stretch or roll out a second piece of dough and make more dumplings.
Once the first two batches are shaped, bring the pot of water back to a vigorous boil and toss in the dumplings. They will sink to the bottom and rise again after 5 to 7 minutes; once they have floated up, boil for another minute. Meanwhile, roll out the other pieces of dough and shape the rest of the dumplings.
Lift the cooked dumplings out of the pot with a slotted spoon and serve immediately in individual bowls or on a serving plate. Serve the sauce of your choice on the side. Cook and serve the remaining dumplings.