Foolproof Berry Pie

In large bowl, with rubber spatula, gently toss strawberries, rhubarb, sugar, flour, tapioca, vanilla and salt. Let stand 30 minutes to soften tapioca, stirring occasionally. (You can use blueberries or raspberries in place of the rhubarb; just be sure to reduce the sugar and sweeten to taste.) Meanwhile, unroll one sheet of dough. Press into a 9 1/2” x 1 1/2” deep-dish pie plate; trim edge, leaving 1 1/2 inches of overhang. (At this point, you can brush the bottom crust with a beaten egg white and refrigerate to prevent sogginess. Preheat oven to 425ºF. Spoon strawberry and rhubarb mixture into crust; sprinkle butter pieces on top. On a lightly floured surface, roll out the remaining sheet of dough into a 12-inch round. Cut dough into 10 3/4-inch-wide strips with a knife. Lay 5 strips across filling, 1 inch apart. Arrange the remaining 5 strips diagonally on top to form a lattice pattern. (You can also weave in strips, if you like.) Trim ends of strips, moisten edge of bottom crust with water and press ends of strips gently to bottom crust to seal. Bring overhang up over strips; pinch edges to seal. Brush lattice (not edge) with milk. Bake pie 50 minutes to 1 hour, or until fruit mixture begins to bubble and crust is golden brown. (If the crust is browning too quickly, shield with strips of aluminum foil.) Let pie stand 1 hour to allow juices to set slightly. Serve warm, or cool pie completely to serve later.