6tablespoons cold unsalted butter cut into 1/4-inch pieces
Pastry: Place the pie shell in the freezer while you make the filling. Preheat the oven to 400F.
Filling: Combine peaches and lemonade concentrate in a large mixing bowl. Set aside for 10 minutes, to juice. Mix cornstarch and sugar in a small bowl then stir into fruit. Scrape filling into chilled pie shell and distribute it evenly, smoothing with a spoon. Place pie on the center oven rack and bake 30 minutes. As the pie bakes, makes the crumble topping.
Topping: Combine flour, pecans, sugar and salt in the bowl of a food processor. Pulse several times to chop the nuts coarsely. Scatter butter over top and pulse again until mixture resembles fine crumbs. Sprinkle milk over mixture and pulse two more times.
Transfer topping to a large bowl and rub it gently between your fingers to make uniform, gravel-like crumbs. Refrigerate.
When pie has baked 30 minutes, remove from oven and spread topping evenly over the pie. “Rake” it around with a fork to spread evenly. Slide pie back into oven and reduce heat to 375F. Bake another 25 minutes, until topping is golden brown and juices bubble up thickly through the crumbs. Transfer pie to cooling rack and cool at least 1 hour before slicing.
Note: Any pastry that fits a 9- or 9 1/2-inch deep-dish pie pan will work. If you have a favorite pastry you prefer, by all means use it.