Blackberry Blueberry Galette with Pistachio Crust

Dough: (makes 2 galettes... you can freeze one for later use)
½ cup raw pistachios
2½ cups all-purpose flour
1 teaspoon kosher salt
1 teaspoon sugar
1 cup (2 sticks) chilled unsalted butter, cut into pieces

Pulse pistachios in a food processor until coarsely ground. Add flour, salt, and sugar and pulse to combine. Add butter and pulse just until a coarse meal forms. With motor running, gradually stream in ½ cup ice water and process until dough comes together. Transfer dough to a work surface; form into a ball, separate into 2 pieces and then flatten each into a disk. Wrap in plastic and chill at least 30 minutes.
Roll out 1 piece of dough on a lightly floured surface to a 10" round; transfer to a parchment-lined baking sheet. *

Filling: (makes one Galette)
5 cups mixture of blueberries and blackberries
Juice of 1/2 a lemon
Zest of 1 lemon 
1/3 cup sugar
2 tablespoons flour
1 large egg, beaten with 1 teaspoon water
Turbinado sugar, for sprinkling

Preheat oven to 400 degrees. Line a rimmed baking sheet with parchment.
In a large bowl, toss the fruit with lemon juice and zest. Add granulated sugar and the 2 tablespoons flour and toss to mix. 
Dump the berries into the center of the dough and spread evenly with your hands, leaving a 2-3 inch border. Fold the edges of the dough up and over the filling, pleating the dough as you fold. Brush the pastry rim with egg wash and sprinkle with the turbinado sugar.
Bake until the fruit is tender, the juices are bubbling and the crust is golden brown, 45-60 minutes. Transfer to a wire rack. Serve with whipped cream or ice cream.