Step 1 Roll out one disk of pie dough according to the instructions in this recipe, until you have a large circle about ⅛-inch thick. Gently roll it over your rolling pin and unroll it over a 9- or 9.5-inch pie dish. Use your hands to press it firmly into the bottom and up the sides. Trim any excess dough so that you have a ½-inch overhang on all sides of the pie pan, then roll the edge of the dough under itself to line up with the rim of the pan. Use your fingers or a fork to crimp. Loosely tent with plastic wrap and refrigerate while you preheat the oven to 425°F.
Step 2 When the oven is hot, uncover the crust and prick the bottom all over with a fork. Line with parchment paper and fill with dried beans or pie weights to reach the top of the crust. Bake for 15 minutes, or until the edges of the crust are set.
Step 3 Remove from the oven and lift the pie weights and parchment paper out of the crust. Bake the crust for another 5 to 8 minutes, or until the bottom is beginning to set. Remove from the oven and set aside to cool slightly.
Step 4 Reduce the oven temperature to 350°F.
Step 5 Place the spinach in a steamer basket and set over a pot filled with 1 inch of water. Bring the water to a simmer, cover, and steam for 1 to 2 minutes, or until the spinach is wilted. Transfer to a kitchen towel and allow to cool slightly, then wring the excess water out of the spinach.
Step 6 In a large bowl, whisk together the eggs and milk. Add the steamed spinach, feta, scallions, salt, and several grinds of pepper and stir to combine. Pour into the par-baked crust. If necessary, use a spatula to smooth the egg mixture into an even layer.
Step 7 Bake the quiche for 40 to 50 minutes, or until the eggs are just set. Allow to cool for 10 minutes before slicing and serving.
