Preparation

1. Cut the butter into thin slices and put in the refrigerator to chill.
2. Mix the flour and salt in a mixing bowl and put in the refrigerator to chill. Also put the water in the refrigerator.

Directions

1. Prepare dough.
   
   1. Whisk the chilled flour to fluff it.
   2. Add the sliced butter, then cut in with a pastry cutter. When the chunks of butter are about pea sized, begin to mix using the sablage method: Scoop up some of the mixture in one hand and rub your other hand across it; the dough should crumble into a parmesan-cheese-like texture. Continue until all the dough is evenly-textured; rub any larger chunks of butter between your fingertips to break them up.
   3. Make a well in the middle of the mixture and pour 3 tablespoons of ice water into it. Using a bench knife or the sharp edge of a spatula, brush the flour into the water and mix using a cutting motion; don’t stir. Continue mixing until it forms crumbly chunks. If it’s too dry, add a little more ice water.

      

   4. Turn the dough out onto an un-floured work surface and work it using the frasisage method: Gather it into a long-ish mound and begin smearing the dough away from yourself along the length of the mound, using short strokes, with the heel of your hand. When you’ve worked across all the dough, gather it together again and repeat once.
   5. Gather the dough into a ball and cover tightly in plastic wrap, then let rest in the refrigerator for at least an hour, up to overnight.
   6. Dust a work surface with flour. Roll the chilled dough out into a disk about 12 inches (30 cm) in diameter, around ¼-inch (5 mm) thick; work the rolling pin from the inside to the outside. If the dough is too stiff to roll, let it sit at room temperature for 15 minutes or so.
   7. Cut a piece of parchment paper to fit a baking sheet, lay the sheet of dough in the middle of it, and refrigerate for 15-30 minutes.
2. Prepare fruit filling.
   
   1. Pit peaches and slice them into ¾-inch (2 cm) wedges.
   2. Mix peaches, blueberries, and 3 to 4 tablespoons of sugar in a bowl; adjust sugar depending on how sweet the fruit is.
3. Assemble.
   
   1. Pile the fruit mixture in the middle of the chilled disk of dough, leaving about 2 inches (5 cm) of dough around the edge.
   2. Pull the side of the dough up and partway over the fruit one bit at a time, folding it under itself every couple of inches (5 cm) to form pleats; there will be a large opening in the top. If the dough is so stiff that there’s a risk of it cracking while folding it, let it sit at room temperature for about ten minutes first.
   3. Brush the top of the crust with cold water to wet it, then dust with 1 tablespoon of sugar; the water is so that the sugar will stick.
4. Bake.
   
   1. Bake at 400°F (200°C) on the lower-middle rack for 50 minutes.
   2. Put the baking sheet on a cake cooler and let it cool for about 10 minutes. Use the parchment paper to slide the galette off of the baking sheet onto the cake cooler, then slide the parchment paper out from under it and let it finish cooling. Serve warm or at room temperature.