Preparation Sift together flour and salt into a chilled large metal bowl. Set a grater in flour mixture and coarsely grate frozen butter into flour, gently lifting flour and tossing to coat butter. Drizzle 5 tablespoons ice water evenly over flour mixture and gently stir with a fork until incorporated. Test mixture by gently squeezing a small handful: When it has the proper texture, it will hold together without crumbling apart. If necessary, add another tablespoon water, stirring until just incorporated and testing again. (If you overwork mixture or add too much water, pastry will be tough.) Gather mixture together and form into a 5-inch square, then chill, wrapped in plastic wrap, until firm, about 30 minutes. (Dough will be lumpy and streaky.) Roll out dough on a floured surface with a floured rolling pin into a 15- by- 8-inch rectangle. Arrange dough with a short side nearest you, then fold dough into thirds like a letter: bottom third up and top third down over dough. Rewrap dough and chill until firm, about 30 minutes. Arrange dough with a short side nearest you on a floured surface and repeat rolling out, folding, and chilling 2 more times. Brush off any excess flour, then wrap dough in plastic wrap and chill at least 1 hour. Cooks' note: