1 1/2pound(s) (4 to 5 medium) peaches, peeled and cut into thick wedges
2 tablespoon(s) butter, cut into small pieces
1 large egg white, lightly beaten
Preheat oven to 425 degrees F. Prepare pastry dough: In medium bowl, mix flour and salt. With pastry blender or 2 knives used scissors-fashion, cut in butter until mixture resembles coarse crumbs. Sprinkle ice water, 1 tablespoon at a time, into flour mixture, mixing with hands until dough holds together (it will feel dry at first). Shape dough into a disk. Wrap in plastic wrap and refrigerate 30 minutes.
Line large cookie sheet with parchment paper. On floured surface, roll dough into 13-inch round (edge may be uneven). Transfer dough round to lined cookie sheet.
Prepare peach-raspberry filling: In large bowl, combine cornstarch and 3/4 cup sugar. Add peaches and raspberries; gently toss to coat fruit.
Spoon filling onto center of dough round, leaving 2 1/2-inch border all around. Dot filling with butter. Fold border of dough up over filling, pleating edges and leaving an opening in center. Pinch dough to seal any cracks. Brush dough with egg white; sprinkle with remaining 1 tablespoon sugar.
Bake galette 45 to 50 minutes or until crust is golden brown and filling is gently bubbling. As soon as galette is done, use long metal spatula to loosen it from parchment to prevent sticking. Cool 15 minutes on cookie sheet, then slide galette onto rack to cool completely.