WONTON, SIU MAI, AND CANTONESE SPRING ROLL SKINS

Steps:

• To make the dough in a food processor, combine the flour and salt in the work bowl and pulse two or three times to blend. Combine the water and egg in a measuring cup and lightly beat. With the machine running, pour the liquid mixture through the feed tube in a thin, steady stream. After all the liquid has been added and the mixture looks crumbly, run the machine for another 20 to 30 seconds, until a large, medium-soft , slightly sticky ball forms (a few crumbly side bits are okay). If the dough doesn't come together, add water by the 1/2 teaspoon. If the dough sticks to the side of the bowl, add flour by the teaspoon to absorb excess moisture. Alternatively, to make the dough by hand, combine the flour and salt in a bowl and then make a well in the center. Lightly beat together the water and egg and then pour into the well. Use a wooden spoon or fork to slowly and steadily stir, moving out from the center toward the rim, to work all the flour into the liquid. Keep stirring as a ragged, slightly sticky mass forms. Then use your fingers to gather and pat the dough together. Add water by the 1/2 teaspoon if the dough feels too stiff or a sprinkling of flour if it is too wet. Regardless of method, transfer the dough and all the bits to a work surface, gather into one ball, and then vigorously knead for about 2 minutes if you used a food processor, or 6 minutes if you made the dough by hand. Properly made dough should be just slightly tacky but not sticky. If the dough sticks to the work surface or your fingers, lightly dust the surface with flour and continue kneading. The finished dough should be fairly smooth and feel as firm as your fingertip. Press on processor dough with a finger, and it should spring back, with no indentation remaining. A faint indention remains on handmade dough, which is not as stiff as its machine-made counterpart. Put the finished dough in a small zip-top bag and expel excess air as you seal it. Set aside at room temperature to rest for at least 1 and up to 3 hours. (The dough can be refrigerated overnight. Return it to room temperature before moving on.)
• To roll out the dough, use a pasta machine. Remove the dough from the bag and cut into 3 equal pieces, replacing 2 of them in the bag and resealing to prevent drying. Flatten a piece of dough with your fingers or a rolling pin to a 1/4-inch-thick rectangle. Use your fingers to dust and then smooth some cornstarch on both sides. Run the dough through the machine at the widest setting (notch 1). Fold the dough into thirds like a letter with one end toward the middle and the other end on top to cover. Press to flatten the dough again so it will easily go through the machine, add another light coating of cornstarch to both sides, and then run it through the machine with one of the unfolded sides entering the rollers first. Repeat the folding, flattening, smoothing, and rolling 3 to 5 times more, until the dough is smooth and elastic. After this initial workout, there's no need to fold the dough again. Set the machine to the next thinnest setting (notch 2). Lightly dust both sides of the dough with cornstarch and then run it through the rollers. Decrease the setting again to notch 3, and pass the dough through once more. Repeat this process 2 more times, reducing the width of the rollers each time and dusting the dough with cornstarch, until the dough is 1/3 2 inch thin. On an Atlas pasta machine, I pause after notch 4 to cut the sheet (now about 18 inches long) in half, lest it become too long and unwieldy. I'm satisfied after notch 5. You should be able to see the shadow of your fingers through the dough when held up in the light.
• The ideal width for the dough sheets is about 6 inches wide. Most home pasta machines yield narrower results so simply put the finished dough sheets on a cornstarch-dusted work surface, smooth the top with more cornstarch, and then use a rolling pin to widen them. Do your best to come close to a 6-inch width. It is fine if the width is not optimal and edges are uneven. When the skins are made into dumplings, imperfections disappear. Put the finished dough sheets on a dry kitchen towel for 8 to 10 minutes, flipping it midway so it dries and firms up enough to easily cut. (If widening the sheets earlier proved difficult, try it after this resting period.) Repeat with the other dough pieces. Cover the finished sheets with a dry kitchen towel.
• To cut the dough sheets, smooth a thin layer of cornstarch over your work surface with your hand. Put the dough on the work surface and smooth a layer of cornstarch on top of it. For Cantonese spring rolls (also known as egg rolls), cut across the sheets at about 6-inch intervals to create large squares. For wontons, use a ruler and sharp knife to cut 3-inch squares. For siu mai, use a 3-inch-round cutter to stamp out as many wrappers as you can from the sheets, dipping the cutter in cornstarch as you work to prevent sticking. Stack the finished skins, wrap them loosely in parchment paper, and put them in an airtight zip-top plastic bag, squeezing out any excess air before you seal the bag. Lay the bag flat on a plate or in a plastic container. Refrigerate for up to 3 days. You can freeze the wrappers, though they are best when fresh. These wrappers may turn grayish in the refrigerator, but their flavor and texture will remain excellent.