-
1
Heat the oven to 350 degrees F and arrange a rack in the middle.
-
2
Place the cookies in a food processor fitted with a blade attachment and process into fine crumbs (you should have about 2 cups).
-
3
Stop the motor, add the melted butter, and pulse to combine.
-
4
(Alternatively, place the cookies in a resealable plastic bag, press out the air, and seal.
-
5
Using a rolling pin, smash into uniform fine crumbs.
-
6
Transfer to a medium bowl, add the melted butter, and mix until evenly combined.)
-
7
Pour the crumb mixture into a 9-1/2-inch deep-dish pie plate and, using the bottom of a cup or your fingers, press firmly and evenly into the bottom and up the sides.
-
8
Bake until fragrant and slightly darkened in color, about 10 to 15 minutes.
-
9
Remove the pie plate to a wire rack and set aside.
-
10
Pour the rum or apple cider into a small bowl and sprinkle the gelatin evenly over the surface; set aside.
-
11
Whisk the pumpkin, milk, brown sugar, egg yolks, spices, and salt together in a medium saucepan over medium heat.
-
12
Cook, whisking constantly, until the mixture just starts to steam and reaches 160 degrees F on an instant-read thermometer, about 8 to 9 minutes (do not let the mixture simmer).
-
13
Remove the pan from the heat, add the rum-gelatin mixture, and whisk until combined and the gelatin has dissolved, about 1 to 2 minutes.
-
14
Transfer the mixture to a large bowl and let cool for 15 minutes.
-
15
Place the egg whites in the bowl of a stand mixer fitted with a whisk attachment.
-
16
Whisk on high speed until medium peaks form, about 1 minute.
-
17
With the mixer still on high speed, slowly add the sugar and continue whisking until stiff, glossy peaks form, about 1 1/2 minutes more.
-
18
Using a rubber spatula, add half of the beaten egg whites to the cooled pumpkin mixture and gently stir until just combined.
-
19
Add the remaining egg whites and gently stir until just combined and no streaks of egg white remain.
-
20
Transfer the chiffon mixture to the prepared pie crust and spread it into an even layer.
-
21
Refrigerate uncovered until set, at least 6 hours or overnight.
-
22
When ready to serve, place the cream, sugar, and rum or apple cider in the bowl of a stand mixer fitted with a whisk attachment.
-
23
Whisk on medium speed until medium peaks form, about 3 minutes.
-
24
Spread evenly over the pie and serve immediately.
