Creating a Nectarine Galette is simple if you follow these easy steps:

1. Prepare the Dough: In a large bowl, mix the flour, sugar, and salt. Add the chilled butter and mix until the mixture resembles coarse crumbs.
2. Add Ice Water: Gradually add ice water, one tablespoon at a time, until the dough comes together. Do not overmix.
3. Chill the Dough: Form the dough into a disk, wrap it in plastic wrap, and refrigerate for at least 30 minutes.
4. Preheat the Oven: Preheat your oven to 400°F (200°C).
5. Prepare the Filling: In a bowl, combine the sliced nectarines, brown sugar, cornstarch, and cinnamon. Toss gently to coat the nectarines evenly.
6. Roll Out the Dough: On a lightly floured surface, roll out the chilled dough into a 12-inch circle. Transfer to a parchment-lined baking sheet.
7. Assemble the Galette: Place the nectarines in the center of the dough, leaving a 2-inch border. Fold the edges of the dough over the nectarines, pleating as you go.
8. Egg Wash: Beat the egg and brush it over the folded dough. Sprinkle coarse sugar on top if desired.
9. Bake: Bake in the preheated oven for 35-40 minutes, or until the crust is golden brown and the nectarines are bubbly.
10. Cool: Remove from the oven and allow to cool for 10-15 minutes before serving.

Follow these steps, and you’ll have an amazing Nectarine Galette ready to impress!