Cut The Butter into tablespoon-size pieces. Put in a food processor and chop by pulsing the machine on and off about 6 times. Add the egg yolk, water and salt and process until the ingredients are mixed, about 5 seconds. The butter should still be in little pieces. Add the flour and process just until the ingredients begin to clump together. Stop processing before a ball forms, or even begins to form. Transfer the dough to a large plastic bag. Working through the bag, press the dough into a ball, then flatten into a disc, about 8 inches wide. If you are using the dough right away, it must be chilled enough to firm it before rolling. Place it in the refrigerator or freezer just until it is firm but not hard. The dough can also be refrigerated for up to 2 days or frozen. If so, let stand at room temperature until softened enough to roll without splitting. 15 minutes before baking, place the rack in the center of the oven and preheat the oven to 400F. Have ready the pie plate or tart pan you will be using. Roll the dough on a floured board to a circle about 1/8-to-1/16-inch thick. Lift the dough several times and brush the board with flour to keep the dough from sticking. Lightly fold the dough in half, then in quarters. Lift to the pie plate or tart pan and position it with the point in the center. Unfold and ease it into the bottom and sides of the pan. Do not stretch the dough. Leave about 3/4 inch of dough beyond the upper edge of the pan and trim the excess. Fold the overlap so there is a double thickness of dough around the sides. Crimp the edge to make a decorative border. Prick the dough with a fork at random, so steam can escape. Refrigerate or freeze briefly, to firm the dough. For a pre-baked shell, line the pastry with aluminum foil and fill the foil with dried beans or rice to weight the pastry. Place on a baking sheet for easier handling. Bake for 14 minutes. Remove the foil with the beans or rice. (The beans or rice can be used over again as weights.) Prick pastry again, and bake until it is lightly colored, 10 to 14 minutes longer. Cool on a wire rack before filling. Sweet

Decrease the salt to 1/4 teaspoon. Makes 1 Crust