Preparation

• Dust a plate with flour. Put the butter and shortening in a single layer on the plate. Refrigerate for 30 minutes. Combine the flour, cornstarch, and salt in a bowl. Refrigerate. Put the vinegar in a 1-cup glass measuring cup. Add enough cold water to equal 1/4 cup liquid. Refrigerate.
• Transfer the flour mixture to a food processor. Pulse several times to combine. Remove the lid, and scatter the butter and shortening over the dry mixture. Give the machine 6 or 7 one-second pulses. The fat should be broken into a random assortment of pieces, from the size of split peas to large gravel.
• Add the water through the feed tube, in a 6- to 7-second stream, giving the machine a series of 6 or 7 one-second pulses as you pour. When you’re done pouring, the mixture will still be crumbly, but if you press a handful of it together in your palm, it should hold together without falling apart. If it doesn’t hold together, pulse for another second.
• 将两块18英寸长的塑料包裹放在柜台上，将它们长约三分之一。将面团混合物倒入塑料的中心。收集并把塑料抓住在相对的两侧。将您的手放在一起以束缚混合物，然后按塑料以压实面团。将手移动到塑料周围，然后再次按下。再重复几次，直到面团不再易碎，然后将面团塑造成3/4英寸厚的磁盘。
• Put the disk on a clean sheet of plastic wrap. Seal in the plastic, and refrigerate for at least 1 hour before rolling. You may also freeze the dough. Slip the wrapped dough into a plastic freezer bag, and freeze for up to 2 months. Thaw overnight in the refrigerator before using.

Variation: Double Crust

• To make enough dough for a double-crust pie or two pie shells, double all of the ingredients, and refrigerate for 30 minutes. After you pulse the dry ingredients in the processor, add slightly more than half of the butter (about half of the total fat). Pulse 6 to 7 times, then add the rest of the fat and pulse 6 or 7 more times. Remove the lid, and then gently fluff the mixture with a fork to loosen it. Replace the lid, and add the water in a 6- to 7-second stream while pulsing the processor. Remove the lid and inspect the dough. If it seems overly dry or if it crumbles when you press some of it in your palm, add an additional tablespoon of cold water. Empty a little less than half of the mixture onto plastic wrap, as directed above. Shape the dough into a 3/4-inch-thick disk. Repeat with the remaining dough (the slightly larger second disk will become a bottom crust).