Cut butter into flour: In a mixing bowl, stir together flour and salt. Toss cold cubed butter in the flour. Use your fingers or a dough cutter to smush the butter into small pea-sized pieces, tossing them in flour occasionally. Work quickly to not warm the butter too much.
Mix in ice water: Make a well in the middle of the flour and pour in the ice-cold water. Mix it all together until it forms a shaggy dough and most of the flour is saturated.
Fold dough: Turn the dough out on top of a sheet of plastic wrap. Use your hands to press the dough together and fold it onto itself about 2 times to create layers of butter. Don’t work the dough too much otherwise it will become tough. You just want it to hold together.
Chill: Form the dough into a flattened disc, wrap with plastic wrap, and chill in the fridge for at least 2 hours.
Make cherry filling: In a medium bowl, stir together the pitted cherries, cornstarch, brown sugar, and vanilla extract until all combined and coated. Set aside.
Prep: Preheat the oven to 350°F and line a baking sheet with parchment paper.
Roll out the dough: Once the dough has been chilled, place it onto a floured surface. Use a rolling pin to roll the dough out until about ⅛” thick, lifting it up and rotating it occasionally to prevent it from sticking to the counter.
Transfer to baking sheet: Transfer the sheet of dough to your lined baking sheet by folding it in quarters and unfolding it on the baking sheet. It’s important to do this now as it will be very hard to pick up later.
Add filling: Pile the cherry mixture onto the middle of the dough, leaving about 2” of empty space around the edges.
Fold over edges: Trim any excess dough that sticks out weirdly if needed. Fold the edges of the dough over onto the cherry filling, overlapping each fold as you work around the galette.
Egg wash: Use a pastry brush to brush a thin layer of beaten egg over all of the dough. Sprinkle with sugar crystals for extra crunch. If your galette has become too warm and soft, chill it in the fridge while the oven finishes preheating.
Bake galette: Bake for 40-45 minutes or until the crust is golden brown and filling is bubbling. Let cool until the bottom of the pan is cool enough to touch with your bare hand. Serve your cherry galette warm with a scoop of ice cream!