1. Prepare the pie crust in two discs according to the recipe and refrigerate for at least 2 hours but up to 2 days. 
2. Preheat the oven to 375 degrees F. Line a baking sheet with parchment paper. 
3. Roll the first disc of pie pastry on a lightly floured surface into a 9-x12-inch rectangle, cutting with the sharp knife any errant edges. 
4. Cut the rectangle into six smaller rectangles. Gently separate the rectangles from the counter and lay them on the prepared baking sheet with at least 2 inches between them. 
5. With a pastry brush, paint each rectangle with the beaten egg. You will have some egg mixture left--set it aside. 
6. Scoop 1 tablespoon of filling onto each rectangle in a thin line down the center. Roll out the second disc of pie pastry, repeating the steps to create six rectangles. 
7. Lay the new batch of rectangles over the rectangles with filling and seal by pressing a fork around the perimeter of each rectangle. Using the pastry brush, paint the tops of each pastry with egg wash and poke several times with the fork. 
8. Bake for 20 to 25 minutes, or until golden. Cool on a wire rack for at least 20 minutes before dusting with powdered sugar or spreading with frosting. 

Basic Pie Crust:

1. Cut the butter into 1/2-inch squares and combine with the flour in a stand mixer bowl. Using your hands, toss the mixture to coat the butter in the flour. Put the bowl in the freezer. In a measuring cup, combine 1/3 cup water, the vinegar, and salt. Stir until the salt dissolves and put the measuring cup in the freezer. Freeze both mixtures for 10 minutes. 
2. Take the mixing bowl out of the freezer and blend the mixture on low speed with the paddle attachment until it starts to become the texture of crumbly meal. Take the measuring cup out of the freezer and, with the mixer still running on low speed, slowly pour the wet mix into the bowl. The dough will be crumbly at first, then after 10 or 20 seconds, it will come together in a ball. Stop the mixer. 
3. Turn the dough out onto the counter and press it together into a large disc. Cut the dough in two equal parts, wrap each piece in waxed paper, and press each into a disc. Refrigerate for at least 1 hour, up to 3 days. 
4. Grease a 9-inch pie dish with butter and give it a light dusting of flour. Take the dough out of the refrigerator 15 minutes before you are ready to roll it out. Unwrap the dough and place one of the discs on a lightly floured counter. Starting from the center, use your rolling pin to shape the dough into a circle about 12 to 14 inches in diameter and 1/4 inch thick. 
5. Fold the crust in half, then fold that semicircle in half again so that you have a quarter of a circle. Line up the corner of the quarter with the center of your pie dish and unfold the quarter into a semicircle, then into the full circle. 
6. Fill the crust with your pie filling. Repeat the rolling process with the second disc of dough, and either lay it on top of the filling, or cut in strips to form a lattice. Use your fingers to crimp the edge of the dough along the circumference of the pie dish.