1. To make the pastry in an electric mixer: In the large howl of an electric mixer on low speed, mix the flours, sugar, and salt for a few seconds to blend them. Stop the mixer, add the butter and shortening, then continue mixing just until the largest pieces are the size of small lima beans, about 20 seconds. They will not all be the same size, and you will still see loose flour. Slowly add the water, 1 tablespoon at a time. Stop mixing as soon as the mixture begins to hold together, about 20 seconds. The dough will form large clumps and pull away from the sides of the bowl, but will not form a ball. It is fine to stop the mixer at any time and squeeze a small piece of dough to check to see if it holds together.

To make the pastry in a food processor: Put the flours, sugar, and salt in a food processor and pulse, several times to blend them. Add the butter pieces and shortening, pulsing just until the largest pieces are about ½ inch in size. Gradually add 3 tablespoons of the water and pulse, adding additional water just until the dough begins to come together in a mass but does not form a ball.