There are two steps in the making of flaky pastry dough. In the first step, the goal is to cut the fat into the dry ingredients, usually with a pastry blender, leaving it in firm, separate pieces, some fine and crumblike and the rest the size of peas. The finer particles of fat coat the grains of flour, partially blocking the penetration of water and hindering the formation of gluten function. When the larger chunks of fat melt during baking, they leave gaps in the dough that fill up with steam and expand, separating the pastry into myriad flaky ledges. Inexperienced pie makers tend to overwork the flour and fat mixture into a soft, greasy paste, resulting in pastry that is mealy and dense, like shortbread, rather than crisp and flaky. The age-old advice remains the best: Have the butter or lard cold (vegetable shortening, which resists melting, may be at room temperature) and work quickly and purposefully.
In the second step, the binding of the dough with water, the trick is to add enough water to make the dough cohere but not so much as to cause gluten to form, which will produce pastry that is either hard or chewy and breadlike. The amount of water required varies depending on the moisture content of the flour, the type of fat used, the degree of blending of fat and flour, and the ambient temperature and humidity. As a general rule, the flour and fat mixture should be moistened only to the point where it forms small balls that hold together when pressed together with your fingers. If the mixture gathers into a mass on its own, without pressure, it is too wet. Beginners should probably err on the side of overmoistening, as a very dry dough will split or crumble when rolled.
About Fats Used in Flaky Pastry Doughs: Vegetable shortening is easy to work with, because it resists melting and disperses easily in dry ingredients. It also has a tenderizing effect on flour and thus assures a tender crust. Shortening, however, has little flavor, and for this reason, use it in combination with unsalted butter if you want more flavor in the crust. The recipe for Flaky Pastry Dough, can be made with either shortening only or with equal parts shortening and butter. For a very buttery crust, make Deluxe Butter Flaky Pastry Dough, which is almost entirely butter. Leaf lard, rendered from the fat of the pig that surrounds the kidneys, produces a wonderfully flaky crust and is traditional for covered fruit pies but is difficult to find. Supermarket lard, which is processed from various parts of the animal, has a more pronounced flavor than leaf lard.
Sweetening and Flavoring Flaky Pastry Doughs: Our basic recipes for Flaky Pastry Dough, below, and Deluxe Butter Flaky Pastry Dough, call for just a hint of sugar. However, both doughs can be sweetened more if you prefer. Except when used in tiny amounts, ordinary granulated sugar makes flaky pastry doughs sticky and hard to handle, so be sure to use powdered sugar instead. One-quarter to 1/3 cup powdered sugar to 2 1/2 cups of flour will impart a light background sweetness; 3/4 cup will make the crust noticeably sweet. Crusts made with more than 3/4 cup powdered sugar may burn and turn out hard and crunchy rather than flaky.
You may flavor any flaky pastry dough by tossing the flour and other dry ingredients with one or more of the following. With all these additions, you should sweeten the dough with at least 1/4 cup powdered sugar. These amounts are for a full recipe of Flaky Pastry Dough or Deluxe Butter Flaky Pastry Dough; use only half as much if you are halving the recipe or if you are making Flaky Cream Cheese Pastry Dough.
Nuts: 1/3 to 1/2 cup coarsely ground or finely chopped
Sesame or poppy seeds: 2 tablespoons
Anise, caraway, or coriander seeds: 1 tablespoon finely crushed
Orange or lemon zest: 1 to 2 teaspoons grated
Cinnamon, ginger, cardamom, or nutmeg: 1/4 teaspoon ground
Moisture-proofing the Crust: Crusts that are to hold uncooked fillings and then be baked should be glazed with egg yolk to prevent sogginess. Crusts filled with cooked mixtures can be glazed with yolk or, if the filling is poured in cold, glazed with one of the following:
Fruit glaze: Melt jelly, jam, or preserves in a small saucepan over low heat, then strain out any solids. Brush the warm glaze over the bottom and the sides of the shell. If you are making a fresh fruit tart, you can daub the fruits on top of the tart with the same glaze that you applied to the shell.
Butter: Unsalted butter makes an effective and virtually unnoticeable protective coat. Soften about 2 teaspoons of unsalted butter to the consistency of mayonnaise, then brush or spread it very thinly over the bottom and sides of the baked shell.
Chocolate: Melt semisweet, bittersweet, milk, or white chocolate and spread it thinly over the inside of the crust with a knife or the back of a spoon. Refrigerate the crust until the chocolate hardens. Moisture-proof shells with chocolate only when its flavor is compatible with the pie or tart filling.
Chocolate Ganache Glaze or Frosting: This is as effective as chocolate in moisture-proofing a shell and, because it is soft, may be applied in a much thicker layer. Banana cream pie, peanut butter pie, and fresh raspberry tarts are particularly good with ganache-glazed shells.
