Preheat the oven to 350 degrees F.
Combine the sugar, 2 tablespoons of the cornstarch and the salt in a large bowl. In a medium bowl, whisk together the buttermilk, dulce de leche and eggs until well combined. Add the egg mixture to the cornstarch mixture and whisk to combine.
Halve and core the pear. Cut lengthwise into 1/4-inch slices. Add the slices to a bowl with the remaining 2 tablespoons cornstarch and toss to completely coat the fruit.
To assemble the pie and bake, place the baked deep-dish pie crust on a baking sheet. Lay the dried apple slices in a single layer on the bottom of the crust. Fan the pear slices out in a circle over the apple slices. Stir any excess cornstarch from the pears into the custard filling and pour the filling over the top of the pears.
Bake the pie until the center is set and the pears are slightly golden brown, about 1 hour. Let cool to room temperature.
Before serving, dust the top of the pie with ground cinnamon. Heat some dulce de leche in a microwave for 30 seconds and stir to loosen. Drizzle over the top of the pie and serve.
In the bowl of a food processor, combine the flour, sugar and salt and pulse to mix. Add the butter and pulse to a coarse meal (the butter should be in pea-size pieces). With the motor running, stream in the water until the dough starts to come together. Dump out the mixture, gather into a ball, press to a disk and wrap well in plastic wrap. Refrigerate for at least 1 hour, and up to overnight.
Spray a 9-inch deep-dish glass pie plate with nonstick cooking spray. Remove the dough from the fridge, unwrap and transfer to a floured surface. Roll out the dough into a 12-inch circle. Transfer the dough to the prepared pie plate. Dock with a fork and crimp the edges between your fingers to make a decorative border, removing any excess dough. Freeze the crust for 20 minutes.
Preheat the oven to 425 degrees F.
Line the crust with a sheet of parchment paper and fill with pie weights or uncooked beans. Bake for 15 minutes. Remove the foil and weights, brush with the beaten egg and continue to bake until the crust is golden brown, about 10 minutes. Let cool completely.
This recipe has been updated and may differ from what was originally published or broadcast.