Step 1

In a small bowl, whisk together the water and cornstarch. Microwave until set, 30 to 40 seconds, stirring halfway through. Chill in the freezer for 10 minutes.

Step 2

Once the cornstarch mixture has chilled, in a food processor, combine the flour, sugar and salt and process until mixed, about 5 seconds. Add the chilled cornstarch mixture and pulse until uniformly ground, about 5 pulses. Add the butter and sour cream and process until the dough comes together and begins to collect around the blade, 20 to 30 seconds. Pat the dough into a 4-inch disc, wrap in plastic wrap and refrigerate for at least 1 hour and up to 48 hours.

Step 3

When ready to bake, heat the oven to 375°F with a rack in the middle position. On a well-floured counter, roll the dough into a 12-inch circle.

Step 4

Hang the dough over the rolling pin and transfer to a 9-inch pie pan. Gently ease the dough into the pan by lifting the edges while pressing down into the corners of the pan. Trim the edges, leaving a ½-inch overhang, then tuck the overhang under itself so the dough is flush with the rim of the pan. Crimp the dough with your fingers or the tines of a fork, then chill in the freezer for 15 minutes.

Step 5

To blind bake, line the chilled crust with foil and fill with pie weights. Bake until the edges are light golden brown, about 25 minutes, rotating the pan halfway through. Remove the foil and weights and bake until the bottom of the crust just begins to color, another 5 to 7 minutes. Let cool on a wire rack for 1 hour before filling. Once baked and cooled, the crust can be wrapped in plastic wrap and kept at room temperature for up to 2 days.