Macerate the berries:
In a medium bowl, combine berries, sugar, and vanilla extract. Stir to combine and allow to macerate until the sugar dissolves and the fruit softenes. Place in the refrigerator until ready to use.
Make the pie crust:
About an hour before you plan to make your pie crust, place the butter cubes in the freezer. The colder the butter, the better your chances of achieving a nice flaky crust.
Once your butter is sufficiently chilled – Place the flour, salt, and sugar in a food processor. I have one of those itty bitty ones for this purpose. Pulse about 5 times until flour, salt, and sugar are combined. Add the butter cubes and pulse until the mixture resembles coarse meal, about 12 pulses total. You should be left with quite a few pea size pieces of butter. And that is cool.
Remove ice from your water, if any – And add 2 tablespoons of water to the food processor and plus 2-3 times. Add water 1 tablespoon at a time, pulsing with each addition. The mixture should just barely clump together at this point, yet have a crumbly look to it. Test by pinching some of the dough and if it comes together, then it’s ready to use. If not, keep adding one tablespoon of water at a time, giving it 2-3 pulses each time. I’ve made this crust many times and it’s never taken more than 4 tablespoons of water. Make sure you don’t add too much; otherwise your crust won’t be flaky.
Turn the crumbly dough over a lightly flour surface and gather it into a rough circle. Handle the dough as carefully as possible so as not to activate too much gluten which can toughen your pie crust. Your pie crust should be dotted with gorgeous pieces of butter. Trust. That is a great thing. Lightly sprinkle flour over surface of the dough. Cover the dough with plastic wrap and place in the refrigerator for at least one hour to chill. If using the dough another day, place in the freezer. When ready to use, defrost it in the refrigerator overnight. Dough keeps well in the freezer for about a month
Assemble and bake the galette:
Preheat the oven to 350 degrees Fahrenheit and set a large cookie sheet on your counter. Tape the corners of a rectangular sheet of parchment paper on your counter and lightly flour it.
Remove the pie dough and macerated betrries from the refrigerator. Turn the dough onto the lightly floured rectangle of parchment paper. Lightly sprinkle the top with flour and with a rolling pin, roll a circle that’s roughly 12-14 inches in diameter and about 1/8 of an inch thick, giving the dough a quarter turn as you roll. To make sure the dough doesn’t stick underneath, lift the dough every couple of turns and lightly sprinkle with flour underneath as needed. If your circle doesn’t turn out perfect, that is OK. We’re not going for perfection here. Place the dough in the refrigerator for about 15 minutes.
After 15 minutes or so remove the pie dough, from the refrigerator.Sprinkle the berries and any juices that accumulated in the center of the pie dough, patting the berries down a bit, leaving about a 2 inch border of pie dough. Fold the border over the fruit, pleating the edges as best you can. Again, it doesn’t have to be perfect. The middle of the galette should remain open. Remove tape from sides of parchment paper and carefully transfer the parchment with the prepared galette onto the cookie sheet. Brush the edges of the galette with beaten egg and sprinkle the surface with granulated sugar.
Place cookie sheet in the oven and bake until the edges of the galette are a nice golden brown, about 25-30 minutes.
Remove galette from the oven and allow to cool slightly, about 5 minutes. Slice and serve with vanilla ice cream if desired.