Cut cold butter into cubes and return to the fridge while preparing the other ingredients.
Put the flour and salt (and sugar, if making a sweet pie) into a food processor.
Put the ice water into a small bowl.
Add the butter to the food processor and pulse until the mixture looks like wet sand.
Begin to add the ice water 1-2 Tbs at a time, pulsing after each addition.
When the dough begins to come together in one lump, it is done.
Divide the dough in half.
Form into a ball with as little handling as possible.
Wrap each ball separately in plastic wrap.
Flatten each dough ball into a thick disk.
Refrigerate for for at least 45 minutes.
When the pie filling is ready, remove the crust from the refrigerator and roll out as usual.