In a medium bowl, combine flour, salt, and sugar. Cut in half of the butter until mixture is crumbly. Toss in remaining butter; cut in until mixture resembles dime-size pieces. (Work quickly so everything stays cold.)

Add 3 tablespoons ice water and vinegar; stir lightly with a fork. Add more water, 1 tablespoon at a time, until dough is evenly moist (holds together when squeezed) but not soaking.

Pat dough into a smooth, round disk. Wrap in plastic and refrigerate for at least 30 minutes, until ready to use.