If you are making a lattice top, use the greater amount of cornstarch suggested to prevent a watery filling from bubbling over the strips. Taste the berries before beginning to determine how much sugar to use.
Pastry Dough (I used flaky cream cheese pastry dough, doubled) 5 cups blueberries, picked over ¾ to 1 cup sugar 3 ½-4 tbs quick-cooking tapioca or cornstarch (use cornstarch for lattice pie) 1 tbs lemon juice 1 tsp lemon zest ⅛ tsp salt 1-2 tbs unsalted butter, cut into small pieces
Roll half the dough into a 13-inch round, fit it into a 9-inch pie pan, and trim the overhanging dough to ¾ inch all around. Refrigerate. Roll the other half of the dough into a 12-inch round for the top crust and refrigerate it. Position a rack in the lower third of the oven. Preheat the oven to 425. Combine the berries, sugar, cornstarch, lemon juice, zest, and salt in a large bowl. Let stand for 15 minutes, occasionally stirring gently. Pour the mixture into the bottom crust and dot with butter. Brush the overhanging edge of the bottom crust with cold water. Cover with the top crust or lattice, then seal the edge, trim, and crimp or flute. If using a closed top crust, cut steam vents. Bake the pie for 30 minutes. Slip a baking sheet beneath it, reduce the oven temperature to 350, and bake until thick juices bubble through the vents, 25-35 minutes more. Let cool completely on a rack. The pie is best the day it is baked, but it can be stored at room temperature for up to one day.
If using frozen berries, be sure that they are individually frozen or dry-packed, meaning that they have been processed without sugar and come in loose pieces rather than a block. Before measuring, be sure to knock off any clinging ice, but do not thaw. Toss the still-frozen fruit with the other ingredients, using the maximum amount of thickening called for, and spoon the filling into the crust at once, without the usual 15-minute standing time. If the fruit is allowed to thaw, it will release a flood of juice and make the crust soggy. Do not glaze the top crust with sugar or egg. Bake the pie at 400 for 50 minutes; then slip a baking sheet beneath it and bake at 350 until thick juices bubble through the vents, 25 to 40 minutes more. The pie I brought hadn’t baked for long enough (hence the blueberry syrup instead of gel). I baked it for 30 minutes (after the initial 50 minutes). When I baked the second pie, I let it bake for the full 40 minutes (plus the initial 50 minutes), and the juices set much better.