A classic summer dessert bursting with juicy berries, this mixed berry pie features a flaky, buttery crust and a sweet-tart filling that's perfect for any occasion.
Make the crust: In a large bowl, whisk together flour, salt, and 1 tablespoon sugar. Cut in cold butter using a pastry blender or your fingers until mixture resembles coarse crumbs with pea-sized butter pieces. Sprinkle ice water over mixture, 1 tablespoon at a time, stirring with a fork until dough just holds together. Divide dough in half, shape into disks, wrap in plastic, and refrigerate for at least 1 hour.
Preheat oven to 400°F (200°C). On a lightly floured surface, roll out one disk of dough to a 12-inch circle. Transfer to a 9-inch pie dish, gently pressing into bottom and sides. Trim excess dough, leaving a 1/2-inch overhang. Refrigerate while preparing filling.
In a large bowl, combine mixed berries, 3/4 cup sugar, cornstarch, lemon juice, and vanilla extract. Toss gently to coat. Let stand for 15 minutes.
Pour berry mixture into the prepared pie crust, mounding slightly in the center. Dot with the 1 tablespoon butter pieces.
Roll out the second dough disk to a 12-inch circle. Cut into 1-inch strips for a lattice top, or place whole on top and cut slits for steam vents. If using lattice, weave strips over filling. Trim and crimp edges to seal. Brush top with beaten egg and sprinkle with coarse sugar.
Place pie on a baking sheet to catch drips. Bake for 20 minutes at 400°F, then reduce oven temperature to 375°F (190°C) and bake for 30-35 minutes more, until crust is golden brown and filling is bubbly. If crust edges brown too quickly, cover with foil or a pie shield.
Cool on a wire rack for at least 2 hours before slicing to allow filling to set.
Tips
For best results, use cold butter and ice water for a flaky crust.
If using frozen berries, do not thaw; add 2 extra tablespoons cornstarch.
Serve warm with vanilla ice cream or whipped cream.
Store leftovers covered at room temperature for up to 2 days.