White Peach Crostata

Pulse the flour, salt, and sugar in a food processor until blended. Add the chunks of butter and blend just until mixture resembles pebbles. Add the ice water, 1 tablespoon at a time, and pulse just until the mixture comes together. Do not let it form a ball. It should should still appear to be pretty pebbly and shaggy.
Turn the dough out onto a lightly floured surface and shape it into a disk. Wrap in plastic wrap and refrigerate for at least 30 minutes or up to 2 days.

In a large bowl, stir together the sugar and cornstarch. Add the peaches, lemon juice, and vanilla. Let stand for about 30 minutes, until the peaches release their juices. Taste and adjust the amount of sugar according to how innately sweet your peaches are.
Preheat the oven to 375°F (190°C). Adjust an oven rack to the center position.
Remove the dough from the refrigerator and let it rest at room temperature for a few minutes. Roll the dough out on a piece of parchment paper to 12 inches in diameter. Transfer the parchment and the dough to a rimmed baking sheet.
Pile the fruit mixture into the center of the dough, spreading it slightly but mounding it in the center. Fold the edges of the dough up around the fruit, allowing the dough to fall into pleats or seams every 2 inches. There should be at least 6 inches of fruit showing in the center of the crostata. Brush the edges of the dough liberally with the beaten egg and sprinkle with sugar.
Bake the crostata for 45 to 50 minutes, until the crust is golden brown and the fruit is bubbling at the edges. If some liquid oozes out during baking, spoon it up and dribble it over the peaches in the center of the crostata.
Transfer the parchment and peach crostata to a wire rack and let cool slightly or, if you can manage to resist, let cool completely. Cut the tart into wedges and serve.