Whisk the flour, sugar, and salt together in a medium bowl. Using a pastry cutter or 2 forks, cut in the butter until the mixture resembles coarse pea-sized crumbs. Add the water and stir until the flour is moistened. Add 1–2 more Tablespoons of water if the dough seems dry. Turn the dough out onto a lightly floured work surface and, using your hands, work the dough into a ball. Flatten it into a thick disc. Wrap the dough disc in plastic wrap or parchment paper and refrigerate it for at least 1 hour, and up to 3 days.

Gently toss the filling ingredients together in a medium bowl until combined. Cover and refrigerate until step 4.

Line a large baking sheet with parchment paper or a silicone baking mat. Clear some shelf space in your refrigerator because the shaped galette must chill in step 6. (See recipe Note below.)

On a lightly floured surface, roll the dough into a 12-inch circle—it doesn’t have to be perfect. Transfer dough to the prepared baking sheet. (You can also roll the dough out right on the parchment paper or silicone baking mat that you are using to line the baking pan. If doing so, lightly flour the parchment paper or baking mat.)

Spoon the fruit and any juices into the center of the dough, leaving a 3-inch border of dough all around the filling. You can simply spoon the filling on, or arrange the pear slices in a more deliberate design, such as concentric circles. Gently fold the edges of the dough over the filling, overlapping the dough as necessary. Press gently to seal the edges. Brush the crust edges generously with egg wash and sprinkle the crust with coarse sugar, if desired.

Refrigerate the shaped galette for at least 15–20 minutes as the oven preheats (next step), and up to 8 hours. If refrigerating for longer than 1–2 hours, cover it lightly. The galette will lose its shape if it’s not cold when it hits the oven.

Preheat oven to 400°F (204°C).

Bake galette until the crust is golden brown, about 30–35 minutes. Cool on the baking sheet for 10 minutes before slicing and serving. Tastes wonderful served warm with vanilla ice cream or whipped cream.

Cover and store leftover galette in the refrigerator for up to 4 days.