Prepare the crust first, because you’ll need to chill it in the refrigerator. Whisk together the flour and salt in a large bowl.
Use a pastry cutter (or a butter knife and your hands) to cut in the cold butter until the mixture has coarse crumbs.
Add four tablespoons of ice water, and mix with a spoon until it starts coming together into a workable dough. Four tablespoons was just enough for my dough, but if it still looks dry, add one tablespoon of water at a time until you reach the right consistency.
Form the dough into a disk, then wrap it tightly in plastic and refrigerate for one hour. You want the butter to be cold so the baked crust turns out flaky.
In a bowl, mix together all of the filling ingredients.
Once your dough has been refrigerated for nearly an hour, preheat the oven to 400 F. Line a baking sheet or a large jelly roll pan (the raised edges will catch escaping juices while the galette cooks) with parchment paper.
Place your dough disk on a lightly floured work surface. Roll the dough out into approximately a 12-inch round. You don’t want any holes or extra thin spots, though, so don’t stretch it too far. Place the rolled dough onto your prepared baking pan.
Add your filling: using your hands, transfer the filling to the center of the galette. Arrange the berries and peaches into a pleasing pattern, leaving about two inches of crust around the edges.
Start at one end and fold the edge over the filling, pleating as you go around. A galette is meant to be rustic, so don’t worry if it doesn’t look perfectly uniform.
Use a pastry brush or sprinkle cold water over the crust. Sprinkle a light dusting of raw sugar over the entire galette.
Bake 35 to 45 minutes, until the crust is lightly golden. (The original recipe called for 25 to 35 minutes, but my galette took longer than 35 minutes.) Allow to cool slightly before cutting and serving