The challenge in making pies and tarts is to cook two very different materials-a barely moist dough and a wet filling-so that the dough ends up very dry and crisp and the filling thick and moist.
For a crust that best resists sogginess from wet fillings, choose a crumbly crust made with egg. Flaky crusts more readily soak up liquid.
To make sure that the crust won't be undercooked and to minimize sogginess, prebake the crust in the pan "blind," without filling. Line the crust with parchment paper and weigh it down with dry beans or ceramic pie weights for part of the prebaking. When weights are removed, "dock" the dough by pressing down with fork tines to prevent blistering. Protect exposed edges from excess heat with strips of kitchen foil or pie guards.
Give the prebaked crust a moisture-resistant coating of beaten egg, chocolate, melted butter, concentrated fruit preserves, or pastry cream, or a layer of moisture-absorbent crumbs. For an egg wash, return the crust to the oven for a few minutes until the coating is dry, then let it cool before filling and baking.
Fresh fruit fillings often release copious liquid and fail to thicken well, especially if the fruit has been sliced.
To control the consistency of a fresh fruit filling, concentrate and thicken the juices before baking. Cut the fruit, toss it with sugar in a colander, and let the juices drain into a bowl. Cook down the juices until thick, recombine them with the fruit and thickener, and fill the crust.
For a translucent fruit filling, thicken the fruit juices with tapioca instead of flour or cornstarch.
Bake fruit pies or tarts near the oven floor, or directly on a baking stone on the floor, to ensure rapid heating of the bottom crust.
Cream and custard pie fillings may fail to thicken in the oven, or may thicken well but then reliquefy.
For cream and custard fillings thickened with eggs and flour or starch, be sure to heat the flour-egg mixture to 180 to 190°F / 80 to 85°C, either before or during baking. Undercooked egg yolks contain an enzyme that breaks down starch and liquefies fillings.
Quiche fillings are easily overcooked and dried out.
Check quiches frequently during baking and remove from the oven as soon as a toothpick or knife tip inserted in the center comes out clean.
Allow quiches to cool until the custard is firm enough to cut without slumping.
Lemon meringue pies often weep liquid from the meringue surface or the bottom, where it floats the meringue from the filling.
Make a stable meringue topping by using powdered sugar that includes cornstarch and placing the meringue on a lemon filling that's still hot. Or make a precooked meringue on the stove top, then place on the pie and finish it in the oven to warm it through and brown the edges.
Ensure a stable lemon filling by cooking the cornstarch-sugar-egg mixture to 180 to 190°F / 80 to 85°C, and adding the lemon juice afterward off the heat.
KEYS TO GOOD COOKING provides simple statements of fact and advice, along with brief explanations that help cooks understand why, and apply that understanding to other situations. Not a cookbook, Keys to Good Cooking is, simply put, a book about how to cook well.
Excerpted from Keys to Good Cooking by Harold McGee Copyright © 2010 by Harold McGee. Excerpted by permission of Doubleday Canada, a division of Random House of Canada Limited. All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.