Combine the flour, salt, and sugar in a food processor and pulse to mix. Add the cold butter and pulse 6–8 times. Add the cold water, a tablespoon at a time, until the mixture begins to clump together.
Remove the dough from the machine and place it in a mound on a clean surface. Divide it in half and gently flatten each half into a disk without over-kneading. Wrap each disk in cling film and refrigerate for at least 1 hour, ideally overnight.