Add flour and salt to food processor work bowl fitted with multi-purpose blade. Pulse for 2 seconds to blend.
Add shortening and butter. Pulse 3-4 times, about 2-3 seconds each time, until mixture is crumbly.
Sprinkle 5 tablespoons ice-cold water over mixture and pulse 1-3 times, about 2-3 seconds each time, until mixture pulls away from sides of work bowl and starts to form a loose ball. If necessary you can add up to 1-2 more tablespoons of water a bit at a time, but don't let it get too wet.
Remove from bowl and form into 2 balls.
On a lightly floured surface, roll each ball into a circle.
Use crusts as directed in your recipe, for one double-crust pie, or two single-crust pies.