This makes enough dough for one 9-inch deep-dish piecrust plus decorative cutouts.

In the bowl of food processor, combine the flour, sugar and salt and pulse to combine. Add the butter and pulse until the mixture resembles coarse meal. Add 6 tablespoons ice water and pulse twice. The dough should hold together when squeezed with your fingers but should not be sticky. If it is still very crumbly, add more water, 1 tablespoon at a time, pulsing twice after each addition.

When ready, turn the dough out onto a work surface and divide into two unequal portions, representing about 2/3 and 1/3 of the dough. Shape each into a disk. Wrap with plastic wrap and refrigerate for about 2 hours. The dough can be made ahead then refrigerated for up to 2 days. 

Remove the dough from the refrigerator and let stand for 5 minutes. Place the larger dough disk between 2 sheets of lightly floured waxed paper and roll out into a 12" round with a thickness of 3/16". Transfer to a greased 9-inch deep-dish pie plate and press the dough into the dish. Trim the edges, leaving a 1/2" overhang. Fold under the excess dough and, using your thumb, decoratively flute the edges.

If you'd like to serve your pie with piecrust cookies, roll out the remaining dough disk in the same manner. Using decorative piecrust cutters, cut out desired cutouts and transfer to a parchment-lined baking sheet.

To bake the piecrust cookies, preheat oven to 375°F. Brush the cutouts with an egg wash (one egg whisked with one tablespoon water) and sprinkle with a mixture of cinnamon & sugar. Bake until golden, for 15 to 20 minutes. Transfer the baking sheet to a wire rack and let cool.

Lightly spoon 1/3 cup flour into a dry measuring cup; level with a knife. Combine 1/3 cup flour, brown sugar, and 1/2 teaspoon cinnamon in a medium bowl; cut in butter and almond paste with a pastry blender or 2 knives until the mixture resembles coarse meal. Place prepared streusel in the refrigerator until needed.

Preheat oven to 325°F. Place the pie dish with the prepared crust on a large baking tray that's been lined with foil or parchment paper. This will prevent any spillover onto the oven floor during baking.

Heat a large nonstick skillet coated with cooking spray over medium heat. Add the sliced apples, 1/4 cup granulated sugar, and 1/2 teaspoon cinnamon; cook 10 minutes or until the apple is tender, stirring the mixture occasionally.  Spoon the apple mixture into prepared crust.

Combine the remaining 3/4 cup granulated sugar, 2 tablespoons flour, salt, and eggs, stirring with a whisk.  Stir in buttermilk and vanilla.  Pour over apple mixture.  Bake at 325º for 30 minutes.  

Reduce oven temperature to 300ºF.  Do not remove the pie from the oven or, if you must, work very quickly. Sprinkle streusel evenly over pie. Return to oven to bake at 300ºF for 45 to 50 minutes, until custard is set. Remove the pie from the oven.

Let stand one hour before serving.