How to Make It
Prepare the Crust: Place flour, sugar, and salt in bowl of a food processor; pulse until combined, 3 to 4 times. Add butter and shortening; pulse until mixture resembles small pebbles, 4 to 5 times. Sprinkle 4 tablespoons of the water over top, and pulse until mixture becomes a shaggy mass, adding additional water, 1 teaspoon at a time, as necessary.
Transfer mixture to a lightly floured surface, and knead until mixture comes together, 3 to 4 times. Divide into 2 pieces (making two-thirds of the dough the first piece and the remaining one-third of dough the second piece). Shape each piece into a disk. Cover each with plastic wrap, and chill 1 hour.
Preheat oven to 400°F. Prepare the bottom Crust: Roll larger disk of dough on a lightly floured work surface into a 12-inch circle, and place into a 9-inch deep-dish pie plate. Fold edge of dough under rim of pie plate. Chill until ready to use.
Prepare the Filling: Combine cherries, sugar, cornstarch, vanilla, and salt in a large bowl, stirring well. Transfer mixture to prepared Crust.
Prepare the top Crust: On a sheet of lightly floured parchment paper, roll remaining disk of dough into a 10-inch circle. Use a paring knife to cut 2 (1-inch-wide) strips from the bottom one-third of the dough, leaving a semicircle of dough on top. Use a 3⁄4-inch star-shaped cutter to cut out stars from the left half of the dough semicircle. Use a paring knife to cut out and remove 3 (1-inch-wide) strips of dough from the right half. Use the parchment to carefully transport and place the prepared semicircle on top of Filling. Place the 2 (1-inch-wide) strips across the uncovered Filling at the bottom of the pie to complete the flag design. Crimp the dough edges.
Whisk together egg yolk and water. Brush entire piecrust with egg mixture. Sprinkle with turbinado sugar. Place pie on a baking sheet lined with aluminum foil.
Bake in preheated oven on lower oven rack 20 minutes. Leaving pie in oven, reduce oven temperature to 350°F, and bake 55 to 60 minutes, until Crust is golden and Filling is bubbly throughout, shielding pie with aluminum foil to prevent overbrowning after 20 to 30 minutes, if needed. Transfer pie from baking sheet to a wire rack, and cool at least 2 hours before serving.