Also known as xiao jiao, these shrimp dumplings, along with char siu bao, shumai, and sesame balls, are the workhorse of a typical dim sum establishment. These are easy enough to make at home on a Saturday evening to serve on Sunday morning, a popular time for Chinese families to partake in dim sum.
*Note: Wheat starch is white in color and looks similar to cornstarch, and is not the same product as wheat flour. It can be found in Chinese or Asian grocery stores and is sometimes sold under the name "non-glutinous flour" or "non-glutinous wheat flour." It can also be found online.
Combine all of the ingredients in a bowl and mix well. Refrigerate.
Combine the wheat starch and salt in a medium-sized glass bowl. Add the hot water and mix well. Cover and set aside for 5 minutes.
Lightly flour a flat work surface. Place the wheat starch mixture on the surface. Add the cornstarch and shortening, and knead until smooth. Cover with a damp cloth and set aside to rest for 15-20 minutes.
To shape the dumplings, roll the wheat starch dough into a 1-inch diameter cylinder. Cut the cylinder crosswise into 1-inch pieces and shape each piece into a ball.
Flatten each ball, by hand or with a tortilla press, to make a 3 ½- to 4-inch circle, keeping the remaining dough covered to prevent drying. Press the edges of the circle firmly with your fingers to thin out the dough.
Place 1 heaping teaspoon of filling in the center of each circle. Fold in half over the filling to make a semicircle. Pinch the curved edges together, pleating one side to the other.
To steam the dumplings, bring water to a rolling boil in a wok. Place the filled dumplings, without crowding, in a steamer. Steam over high heat until the dumplings appear translucent, about 5 minutes. Remove from the heat and let stand for 1 minute before serving. Serve with soy sauce and chile sauce or mustard for dipping.