This is the French version of classic pie or tart pastry.
Combine flour, salt, and sugar in food processor. Add butter; process until mixture resembles coarse meal, about 8 to 10 seconds. For hand method, place dry ingredients in large bowl. Add butter; blend with pastry cutter until mixture resembles coarse meal.
Add ice water in a slow steady stream through feed tube of food processor with machine running, until dough holds together for no longer than 30 seconds. For hand method, mix dough with a wooden spoon, adding water until dough just holds together.
Turn dough onto piece of plastic wrap. Press into flat circle, and wrap it in plastic; refrigerate at least 1 hour. May be frozen, double wrapped in plastic, for several months.