2-1/2 cups all-purpose flour
1/4 teaspoon salt
1 cup cold butter, cubed
6 to 8 tablespoons ice water
FILLING:
1 cup sugar
1/4 cup cornstarch
Dash salt
1/3 cup water
1/2 teaspoon ground cinnamon, optional
1 cup fresh blueberries
1 cup fresh raspberries
1 cup halved fresh strawberries
3/4 cup fresh blackberries
1 tablespoon lemon juice
2 tablespoons butter

In a large bowl, mix flour and salt; cut in butter until crumbly. Gradually add ice water, tossing with a fork until dough holds together when pressed. Divide dough into two portions so that one is slightly larger than the other. Shape each into a disk; wrap in plastic wrap. Refrigerate 1 hour or overnight.

For filling, in a large saucepan, whisk sugar, cornstarch, salt, water and, if desired, cinnamon until smooth; add blueberries. Bring to a boil; cook and stir 2 minutes or until thickened. Cool slightly.

Preheat oven to 400°. Gently fold raspberries, strawberries, blackberries and lemon juice into blueberry mixture. On a lightly floured surface, roll out larger portion of dough to a 1/8-in.-thick circle; transfer to a 9-in. pie plate. Trim pastry to 1/2 in. beyond rim of plate. Add filling; dot with butter.

Roll remaining dough to a 1/8-in.-thick circle; cut into 1/2-in.-wide strips. Arrange over filling in a lattice pattern. Trim and seal strips to edge of bottom pastry; flute edge. Bake 10 minutes.

Reduce oven setting to 350°; bake 45-50 minutes or until crust is golden brown and filling is bubbly. Cool on a wire rack. Yield: 8 servings.

Source[www.tasteofhome.com]