1. In a food processor, combine the flour and salt. Add the chilled butter cubes and pulse until the mixture resembles coarse crumbs.

2. Add the ice water and pulse until the dough just begins to come together. Dump the dough onto a lightly floured surface and gently shape it into a disk. Wrap in plastic and refrigerate for at least 1 hour.

3. Preheat the oven to 400°F (200°C). Line a baking sheet with parchment paper.

4. In a large bowl, toss the peach slices with the sugar and cornstarch until well coated.

5. On a lightly floured surface, roll the chilled dough into a 12-inch circle, about 1/4-inch thick. Transfer the dough to the prepared baking sheet.

6. Arrange the peach slices in the center of the dough, leaving a 2-inch border. Sprinkle the chopped basil over the peaches.

7. Fold the dough border over the peaches, pleating it as you go. Brush the dough with the egg wash.

8. Bake for 30-35 minutes, until the crust is golden brown and the peaches are bubbly. Allow to cool for 10 minutes before serving.