Apple Custard Pie with Hazelnut Streusel

The Steps

1. To make the crust, combine flour, sugar, baking powder, and salt in the bowl of a food processor. Pulse to blend. Add the butter and pulse until pea-size crumbs form. Pour the water over the flour mixture and pulse until the dough just starts to come together.
2. The dough will be dry and clumpy at this stage. Dump the mixture onto a clean work surface and start to bring the dough together by hand. Begin by pressing the dough firmly with the heel of your palm, squeezing the dough until it begins to hold together. Repeat the process until the dough forms a ball. Press the dough into a 1-inch thick disc. You should still see pea-size bits of butter running throughout the dough. Place the dough in the refrigerator to chill for at least 1 hour. The dough can be made 3 days in advance.
3. When you’re ready to roll out the dough, if refrigerated for longer than 1 hour, allow the dough to rest at room temperature for 5-10 minutes.
4. Preheat oven to 375 degrees. F. Lightly grease and 9-inch pie plate.
5. On a lightly floured surface, roll the dough into a 12-inch disc. Line the 9-inch pie plate with the dough and trim so it lays about a ½ inch beyond the pan. Crimp the edges. Place the pie plate in the freezer while you assemble the rest of the layers.
6. To make the apple filling, peel, core, and halve the apples. Thinly slice the apples. In a large skillet, melt the butter over medium heat. Add the sliced apples, brown sugar, rum, cinnamon, and salt. Cook over medium heat for 5 minutes. Increase the heat to medium-high and cook, allowing the mixture to bubble and the sauce to reduce slightly, about 8-10 minutes. Take the mixture off of the heat and set aside.
7. In a large bowl, add the heavy cream, sour cream, and sugar. Whisk to combine. Add the egg yolks and vanilla bean paste and whisk until thoroughly combined. Whisk in the all-purpose flour until smooth and no lumps remain.
8. Remove the pie plate from the freezer. Pour the apple mixture into the bottom of the unbaked pie crust. Pour the custard over the apples. Place the pie on a baking sheet and bake for 25 minutes.
9. While the pie is baking, make the streusel by combining flour, brown sugar, cinnamon, salt, and hazelnuts in a bowl. Using a fork, cut in the softened butter until pea-sized crumbs form. Place the mixture in the refrigerator until ready to use.
10. Remove the pie from the oven and top with the streusel mixture. Place the pie back in the oven and bake for an additional 20-25 minutes, or until the streusel is golden brown and center gives a slight jiggle.
11. While the pie finishes baking, make the whipped cream. Add the cream and sugar to the bowl of a stand mixer fitted with the whisk attachment. Beat on high until the mixture just starts to thicken. Add the vanilla extract, cinnamon, and whiskey. Continue to beat at high speed until soft peaks form. Transfer the mixture to an airtight container and refrigerate until ready to use.
12. Allow the pie to rest at room temperature for at least an hour before slicing. Top with whipped cream before serving.