YIELD: Makes 24 dumplings
ACTIVE TIME: 1 1/2 hr
TOTAL TIME: 1 1/2 hr
Stir together 1 1/2 cups flour and lukewarm water (1/2 cup) in a bowl until a shaggy dough forms. Knead on a lightly floured surface, adding more flour as needed if dough is sticky, until smooth, about 1 to 2 minutes. Dust dough lightly with flour and cover with an inverted bowl, then let stand at room temperature at least 10 minutes and up to 1 hour (to let gluten relax).
If using fresh water chestnuts, scrub very well, then peel with a sharp paring knife and rinse. Cover fresh water chestnuts with 1 1/2 cups water in a 1-quart saucepan and bring to a boil, then boil until chestnuts are crisp-tender and slightly translucent, about 5 minutes. Drain in a colander and rinse under cold water to cool.
Cut fresh or canned water chestnuts into 1/4-inch dice and put in a medium bowl along with shrimp, pork, scallions, soy sauce, ginger, and sesame oil. Knead mixture with your hands until just combined, then chill, covered, 10 minutes.
While shrimp mixture chills, line a large baking sheet with paper towels and dust lightly with flour, then lightly dust work surface with flour. Halve dough and cover 1 half with inverted bowl. Pat remaining half into a flat square, then roll out into a 13-inch square (less than 1/8 inch thick) with a lightly floured rolling pin, dusting work surface with additional flour as needed. Cut out 12 rounds, very close together, using cutter. (If dough sticks to cutter, lightly dip cutter in flour and shake off excess). Reroll scraps if necessary.
Transfer rounds to lined baking sheet and cover loosely with another layer of paper towels lightly dusted (on top) with flour. Roll out remaining half of dough and cut out 12 more rounds in same manner, then transfer rounds to top layer of paper towels.
Line another large baking sheet with paper towels and dust lightly with flour. With your hand palm-up, put 1 dough round on fingers near palm, then put 1 tablespoon pork mixture in center of round and fold it over filling to form an open half-moon shape. With a wet finger, moisten border along lower inner edge of round. Using thumb and forefinger of one hand, form 10 to 12 tiny pleats along unmoistened edge of dumpling skin, pressing pleats against moistened border to enclose filling. The moistened border will stay smooth and will automatically curve in a semicircle. Stand dumpling on a baking sheet and form 23 more dumplings in same manner (you may have some filling left over), arranging them in 1 layer, about 1/2 inch apart. Cover loosely with paper towels.
Stir together soy sauce, vinegar, water, and chile oil in a small bowl. Restir just before serving.
Heat vegetable oil in a 10-inch nonstick skillet over moderately high heat until hot but not smoking, then arrange 7 dumplings, seam sides up, in a tight spiral pattern in center of skillet. Arrange remaining 17 dumplings along outer edge (they should touch one another). Fry dumplings until bottoms are pale golden, 2 to 3 minutes. Add 1/2 cup water, tilting skillet to distribute, then cover tightly with a lid and cook until liquid is evaporated and bottoms of dumplings are crisp and golden, 7 to 10 minutes. (Use a spatula to loosen and lift edges to check bottoms; replace lid and continue cooking if necessary, checking after 1 to 2 minutes.) Remove lid and invert a large plate with a rim over skillet. Using pot holders and holding plate and skillet tightly together, invert dumplings onto plate. Serve dumplings immediately, with dipping sauce.
·Dumplings can be formed (but not cooked) 1 day ahead. Chill in 1 layer on lightly floured paper towels, not touching and loosely covered with more paper towels, in an airtight container.
·Sauce can be made 3 hours ahead and kept at room temperature.