Step 1Make the crust: Mix the sugar and salt into 1/3 cup water in a liquid measuring cup until both dissolve. Freeze to chill. Meanwhile, put the flour in a large bowl. Add the butter and duck fat and toss to coat. Use your fingers to quickly press the butter and fat into the flour until flattened and the mixture resembles coarse meal with ragged clumps. Add the chilled water mixture all at once. Rake the mixture with your fingers spread wide until the dough comes together into a shaggy mass and no dry bits remain.
Step 2Gather the dough into two balls, one slightly larger than the other, and press into 1-inch-thick disks. Wrap each tightly in plastic wrap. Refrigerate until firm, about 1 hour.
Step 3Arrange a rack in the lowest position of the oven and heat the oven to 450 degrees. Flour a work surface and rolling pin. Unwrap the larger disk of dough, place on the surface, and sprinkle with flour. Roll the dough into a 12-inch round, rotating after each roll and re-flouring the surface, dough and pin as needed to prevent sticking. Gently roll the dough onto the pin, then unroll into a 9-inch regular (not deep-dish) pie dish, centering it. Gently ease the dough into the edges of the dish. Refrigerate to firm up.
Step 4Flour a large sheet of parchment paper and the pin again. Repeat the rolling with the smaller disk of dough, using the floured parchment as your work surface. Slide onto a baking sheet and refrigerate.
Step 5Make the filling: Whisk the sugar, cornstarch and salt in a large bowl. Add the peaches and lemon juice and toss until evenly coated.
Step 6Scrape the peach mixture into the pie dough in the dish and spread evenly. Flip the other pie dough on the parchment over the filling, centering it, then remove the parchment. Use kitchen scissors to trim the edges ½ inch beyond the dish’s rim. Gently fold the edges together and tuck them under so that they’re flush with the rim. Lightly pinch and crimp the edges as you’d like. Cut three slits in the top pie dough.
Step 7Line a rimmed baking sheet with parchment paper or foil. Put the pie on it, then slide onto the lowest rack of the oven. Bake until the crust is set and golden, about 30 minutes. Lower the oven temperature to 350 degrees and continue baking until the crust is golden brown and the filling is bubbling through the slits, about 45 minutes longer. If the top of the pie starts to get too dark, tent it loosely with foil.
Step 8Cool the pie completely on the baking sheet on a wire rack before slicing and serving.
Summer Fruit Pie
Substitute 6 cups of a mixture of ripe summer fruit, such as blueberries, blackberries, raspberries and cut nectarines, plums or apricots, for the peaches.
Lattice Fruit Pie
After rolling the top dough disk, cut it into 1-inch-wide strips. Lay half the strips across the pie in one direction. Place the remaining strips in the opposite direction, one at a time, weaving them through alternating dough strips.