Okay, let's get this out of the way upfront: This is not a gnarly guide for those who want to up their dietary fiber or cut calories. This is a recipe for those who want to put whole wheat flour into a pie crust for flavor rather than health. And if the flavor of whole wheat doesn't strike your fancy, then maybe it's time to go ahead and click on through to this article on cake.
Whole wheat flour is the defining magic of a graham cracker, the irresistible nuttiness of a bran muffin, the subtle crunch of a digestive biscuit, and the toasty sweetness of a Wheat Thin (homemade or otherwise). Put all those qualities into a pie dough, and you've got the perfect foundation for anything from apple turnovers to chicken pot pie.
If you've made my Old Fashioned, Flaky Pie Dough, then you'll notice that the method and ingredients are very similar. What's different is the 50/50 blend of whole wheat and all-purpose flour. Because whole wheat flour inhibits gluten development and can soak up far more water than all-purpose, the recipe requires a few minor tweaks.
First, to account for the tenderness whole wheat flour naturally brings to the table, the butter is reduced by 25%. That makes it a little easier for gluten to form, which makes the dough supple and strong so it doesn't tear or crumble apart. Second, to account for the absorbency of whole wheat flour, the water is increased by 25%. That makes it a bit easier for gluten to form, but it also ensures there's enough moisture to form a smooth and pliable dough.
Aside from those changes, the technique remains the same overall. Start by whisking the whole wheat and all-purpose flours together with a bit of salt and sugar (I recommend using sugar even for savory jobs, as it improves crispness and browning, while also helping to round out the flavor of the crust).
If it's warm in your kitchen, say, over 73°F, be sure to consult this guide to navigating room temperature before proceeding to the next step. If the flour in the bowl is warm, it will transfer heat to the butter, and your dough will be a mess.
But, assuming your flour is reasonably cool, or that you've taken steps to make it so, you won't run into any trouble at all.
Add the butter in big, 1/2-inch cubes, and then smash each one between your thumb and forefinger, like popping bubble wrap. You don't want to rub the butter into the flour, or form pea-sized bits, or work it into a mealy mix. Nothing like that at all! The goal is simply to create a bunch of big, flattish chunks of butter that will translate into a super flaky dough. Overwork the butter, and your crust will be mealy and crumbly without any flake at all.
After smashing the butter, stir in the water, then knead the dough against the sides of the bowl until it comes together in a rough ball. Rough being the operative word—if kneaded until smooth, the butter will be overworked and those chunky pieces will disappear.
Using all the whole wheat flour you need (seriously, don't skimp), roll the dough until it's about 10- by 15-inches. If the dough is sticking to the counter or your rolling pin, that just means you're not using enough flour. Be generous! Excess flour can be brushed off later on. Once the dough is rolled out, bring each 10-inch side toward the middle, then close both sides together like a menu, and fold the whole thing in half (top to bottom).
Unlike a fancy puff pastry or croissant dough, this sort of folding isn't about precision, it's about throwing in a few quick and dirty layers that will be thinned and lengthened as you roll out the top and bottom crusts later on. For that modicum of effort, you'll be rewarded with tons of flaky layers.
Next, divide the block of dough in half.
If it feels soft or sticky, chill the dough until the butter begins to firm, about 30 minutes or so if your kitchen is warm. Otherwise, go ahead and roll each portion of dough as needed, whether as two 9-inch pies, or as the top and bottom crust of a single pie. Whatever the case, the dough absolutely must be refrigerated two hours before baking in order to relax the gluten and chill the butter to preserve the layers. If this process is rushed, the crust will have a greasy, mealy consistency. This is true even if you refrigerate the blocks of dough to roll at another time; the dough will always need 2 hours to chill after rolling and shaping (whether that's a simple lattice or a fancy herringbone design).
However you shape it, this dough holds its form well in the oven, and bakes up tender, flaky, and crisp, but instead of the buttery simplicity of a classic pie crust it has the hearty, nutty flavor of whole wheat. That makes it a perfect match for autumnal flavors like apple and pecan, as well as the perfect counterpoint to super rich or tangy flavors like cream cheese and key lime.