How to Make It
In the bowl of a stand mixer fitted with the paddle, combine the flour, sugar and salt and mix at low speed. Add the butter and mix at medium speed until almost incorporated, with some pecan-size pieces remaining, about 1 minute. In a small bowl, whisk the egg yolks with the milk. With the machine on, drizzle the egg mixture into the flour mixture and mix until the pastry just starts to come together, about 30 seconds; it will be crumbly. Scrape the pastry onto a lightly floured work surface and gather it together. Using the heel of your hand, smear the pastry against the work surface to work in the butter. Form the pastry into a 1-inch-thick disk, cover in plastic wrap and refrigerate until firm, at least 1 hour.
Preheat the oven to 350°. Grease an 8-inch-square baking pan with baking spray and line with parchment paper, leaving 3 inches of overhang on all sides.
Cut one-third of the pastry off of the disk. On a lightly floured surface, using a lightly floured rolling pin, roll out the smaller piece of pastry to an 8-inch square; transfer to a parchment paper–lined baking sheet and refrigerate. Roll out the larger piece of pastry to a 12-inch square, about 1/4 inch thick. Ease the pastry into the prepared pan, pressing it into the corners and up the sides; trim the excess pastry, leaving no overhang. Line the pastry with parchment paper and fill with pie weights. Bake for about 30 minutes, until just pale golden and set. Remove the pie weights and parchment paper. Transfer the pan to a rack and let the crust cool completely.
In a medium bowl, toss the strawberries with the granulated sugar, cornstarch, orange zest and salt. Spread the filling in the pastry crust. Cover with the chilled piece of pastry crust, gently pressing it down around the edges. Brush the top with the beaten egg and sprinkle with the sanding sugar. Using a sharp paring knife, make six 2-inch-long slits in the top pastry. Bake for about 50 minutes, until the crust is deep golden. Transfer the pan to a rack to cool, at least 3 hours. Carefully lift the pie out of the pan and transfer to a platter before serving.