For the crust:
3 cups all-purpose flour
1 teaspoon kosher salt
1 tablespoon granulated sugar
1/2 cup (1 stick) butter, cut into small cubes and chilled
1/2 cup vegetable shortening, cut into small cubes and chilled
1 large egg
1 tablespoon white distilled vinegar
5 to 7 tablespoons ice water
For the streusel topping:
1 cup rolled oats
1 cup firmly packed light brown sugar
1/2 cup all-purpose flour
1/2 cup (1 stick) butter, cut into small cubes and chilled
1/2 cup coarsely broken pecan halves
1/4 cup finely chopped crystallized ginger
For the pumpkin filling:
6 large eggs
1 1/2 cups granulated sugar
2 tablespoons cornstarch
2 teaspoons ground cinnamon
1 teaspoon ground ginger
1/2 teaspoon ground cloves
1/2 teaspoon ground nutmeg
1 teaspoon kosher salt
2 (15-ounce) cans pure pumpkin purée or 3 1/2 cups homemade pumpkin purée (Recipe follows)
1 cup heavy cream
To make the crust: Place the flour, salt, and sugar in the bowl of a food processor and pulse to combine. Scatter the cubes of butter and shortening over the flour and pulse until the mixture resembles wet sand with a few pieces of fat the size of small peas.
Whisk together the egg, vinegar, and 5 tablespoons of the ice water in a small bowl until well-blended. Pour over the flour mixture and pulse to form large clumps of dough; if it doesn’t hold together, sprinkle in more ice water, 1 tablespoon at a time, and pulse only until incorporated. Pour the clumps onto a work surface and gather into a smooth ball.
Press the dough evenly across the bottom and up the sides of a 17 1/2- x 11 1/2- x 1-inch rimmed baking sheet (half sheet pan). Use your fingers or the bottom edge of a metal measuring cup to press the dough evenly into the pan and against the edges — the edges should be straight, not sloped. Cover with plastic wrap. Refrigerate for at least 30 minutes and up to 1 day.
To make the streusel: Stir together the oats, brown sugar, and flour in a large bowl. Work in the butter with a pastry blender or fingertips until the mixture is crumbly. Pinch together about one-third of the mixture into balls the size of a marble; leave the rest crumbly. Gently stir in the pecans and ginger. Cover and refrigerate until the butter is firm, at least 30 minutes.
To make the filling and bake the pie: Preheat the oven to 350ºF. Whisk together the eggs, sugar, cornstarc