Cut the butter into small pieces. Chill the butter, flours, and shortening in the freezer until very cold. Put the flours, salt, and butter into the bowl of a food processor and pulse a few times to cut the butter into pieces the size of small peas. The mixture should be very lumpy. If in doubt, error on the conservative side and do not over process. Add the cold shortening to the bowl and drizzle in the water a little at a time while pulsing the machine. Stop adding water and pulsing when the dough forms lumps the size of English walnuts. Do not mix until the dough comes together in a ball!

Dump the contents of the bowl onto a floured surface and smear the lumps with the heel of you hand. Gather the dough into a ball and flatten into a disk. Wrap with plastic film and refrigerate for 30 minutes or up to two days.

Remove the dough from the refrigerator and let warm for a few minutes if necessary. Cut into two pieces and roll each piece on a floured surface, rotating and lifting the dough often so it doesn't stick to the surface.