Bourbon Sweet Potato Pie

In a food processor, combine the flour, sugar, salt, and cinnamon. Add the butter cubes and pulse until crumbly. With the food processor running, drizzle in just enough water, 1 tablespoon at a time, to bring the dough together into a ball.
Turn out the dough onto a sheet of plastic wrap, shape into a disc, and wrap well. Refrigerate for 30 minutes.
Turn out the dough on a lightly floured surface and roll it into a 12-inch (30 cm) circle. Lightly butter a 9-inch (23-cm) pie pan. Gently lift an edge of the dough and drape it over the rolling pin and then carefully move it over the pie pan. Gently lower and press the dough into the pan and then flute the edges. Place the pie pan in the refrigerator while preparing the filling and crumble.
In a small bowl, lightly whisk the egg and milk until combined and set aside until just before baking the pie.
Preheat the oven to 350°F (175°C) and position a rack in the lower third of the oven.

In the food processor, briefly mix the brown sugar, flour, cinnamon, salt, and pecans to combine. Scatter the butter cubes evenly over the sugar mixture and pulse just until the mixture is crumbly. (Alternatively, in a medium bowl, use a pastry cutter or two knives to cut the butter into the dry ingredients until the mixture is crumbly.)

In the bowl of a stand mixer or a large bowl, combine the mashed sweet potato, brown sugar, and corn syrup. Using the stand mixer or an electric hand-held mixer, beat until well blended and no lumps remain, at least 1 minute.
Add the bourbon, cinnamon, nutmeg, ginger, salt, and vanilla and beat 1 minute more. Add the eggs and heavy cream and mix until incorporated.

Remove the pie pan from the refrigerator and use a pastry brush to lightly brush some of the reserved egg wash over the rim of the crust. Pour the sweet potato filling into the crust. Top with a generous layer of streusel. (Chances are you’ll have some streusel left over. If you don’t nibble it all, you can freeze the rest to sprinkle on your next batch of muffins or your next bowl of oatmeal.)
Place the pie on a rimmed baking sheet lined with foil and slide it on the lower rack of the oven. Bake the pie until the crust and streusel are golden brown, the edges of the filling are set, and the center jiggles just slightly, 55 to 60 minutes. Let the pie cool completely before serving.