Mixed Berry Galette

1. Prepare the galette dough a few hours before you need it. Mix the salt into your very cold water. Cut your very cold butter into 1-inch pieces (I like to stick it in the freezer right before using it).
2. Add the flour and butter pieces to a food processor, and pulse until butter is in pea-sized pieces. Drizzle in the cold salted water and pulse until a ball forms. Transfer to a flour-lined work surface, and form into a 1-inch thick disk with your hands. Wrap with plastic, and chill in the fridge for at least 2 hours. Let cool slightly before working with the dough.
3. Preheat oven to 400 F. When you’re ready to use the dough, use a rolling pin to shape it into a rough circle, about 1/8 inch thick. It’s okay if the shape isn’t perfect. Transfer the dough carefully to a parchment paper-lined baking sheet.
4. Add the berries to a large bowl, and toss with maple syrup, lemon zest, and corn starch. Arrange the berry mixture in the center of the dough, allowing a 3-inch border for the crust. Fold the edges of the dough up and over the filling, pleating the dough as you go around. Brush the crust with the beaten egg, and sprinkle the crust and filling with some sugar. Bake for about 30 minutes until crust is golden. Top with vanilla ice cream, and serve!