Preheat the oven to 375°F and prepare a baking sheet with parchment paper. In a large bowl combine all the filling ingredients and gently stir to combine.
Place the chilled dough on a lightly floured surface and roll it out with a rolling pin. Start in the middle and work out and get to the desired thickness and size (about ¼' thick and 10-12" in diameter). Be careful not to stretch the dough. You just need a rough circle or rectangle so don't be too picky. Remember, galettes are "rustic"!
Place the rolled-out dough onto the prepared baking sheet. Gently spoon the mango filling in the middle, leaving 1-2" of dough all around the edges. Fold the edges of the dough over the filling all the way around. Don't worry about being perfect or even, just make sure all the filling stays put. Whisk the egg and brush it on the crust edges. Sprinkle the egg wash generously with brown sugar.
Bake for 45-50 minutes or until the filling is bubbling and the crust is golden brown. I enjoy a slightly burnt sugar crust but you can pull the galette out before the sugar it gets too dark. Allow the galette to cool before serving, but this is best served warm. Enjoy!
Choose the Right Fruit: Select ripe mangos when making a galette for the best results and sweetest flavor.
Preparing the Fruit: As I mentioned, galettes are meant to be rustic so you don't have to have perfectly cut mango pieces. However, ensure you make similar-sized pieces so the filling stays in place and for a more manageable bite when enjoying.
Rolling Out the Dough: Roll out the galette dough on a lightly floured surface to a roughly circular shape, about ¼ inch thick. If the dough becomes too soft, you can refrigerate it for a short while to firm it up.
Leaving a Border: Leave a border of about 1-2 inches around the edges of the rolled-out dough. This border will be folded over the fruit filling to create the rustic, free-form shape of the galette.
Filling Placement: Arrange the fruit slices or chunks in the center of the rolled-out dough, leaving the border empty.
Folding and Crimping: Fold the border of the dough over the fruit filling, gently pleating and crimping the edges as you go. This will help contain the fruit and give the galette its rustic appearance.
Brush with Egg Wash: Before baking, brush the exposed dough with an egg wash. This will give the galette a beautiful golden-brown color and a slightly glossy finish.
Cooling and Serving: Allow the galette to cool before serving. You can serve it warm or at room temperature, and it pairs well with a scoop of ice cream or a dollop of whipped cream.