Deep-Dish Blackberry-Peach Double-Crust Pie

1. 1If you haven’t already, prepare the pastry and refrigerate until firm enough to roll, about 1 hour.
2. 2While the pastry chills, blanch the peaches. After you slip off the skins, slice the peaches into a large measuring cup; you’ll need 4 cups. (Reserve any remaining peaches for another use.) Combine the sliced peaches, blackberries, and 1/2 cup of the sugar in a large bowl. Toss well to combine and set aside for 15 minutes.
3. 3On a sheet of lightly floured waxed paper, roll the larger portion of the pastry into a 13 1/2-inch circle with a floured rolling pin. Invert the pastry over a 9 1/2- to 10-inch extra-deep-dish pie pan, center, and peel off the paper. Gently tuck the pastry into the pan, without stretching it, and let the overhang drape over the edge. Place in the refrigerator for 15 minutes.
4. 4In a small bowl, mix the remaining 3 tablespoons sugar with the cornstarch. Stir the mixture into the fruit along with the nutmeg, lemon juice and lemon zest. Preheat the oven to 400°F.
5. 5On another sheet of lightly floured waxed paper, roll the other half of the pastry into an 11 1/2-inch circle. Turn the filling into the chilled pie shell. Smooth the fruit with a spoon and dot with the butter. Lightly moisten the rim of the pie shell. Invert the top pastry over the filling, center, and peel off the paper. Press the top and bottom pastries together along the dampened edge. Trim the pastry with scissors or a pairing knife, leaving an even 1/2-inch overhang all around, then sculpt the overhang into an upstanding ridge. Poke several steam vents in the top of the pie with a fork or pairing knife. Put a couple of the vents near the edge of the crust so you can check the juices there later. To glaze the pie, lightly brush the pastry with milk and sprinkle with sugar.
6. 6Place the pie on the center oven rack and bake for 30 minutes. Reduce the oven temperature to 375°F and rotate the pie 180 degrees, so that the part that faced the back of the oven now faces forward. Just in case, slide a large aluminum foil-lined baking sheet onto the rack below to catch any drips. Continue to bake until the juices bubble thickly at the steam vents and the top is golden brown, 35 to 45 minutes. If the top starts to get too dark, cover it with loosely tented aluminum foil during the last 15 minutes.
7. 7Transfer the pie to a wire rack and let cool for at least 2 hours before serving.

Excerpted from Pie, by Ken Haedrich. © 2004, used by permission from The Harvard Common Press.