Preheat oven to 275°. Place crackers in a deep pie dish (a shallower one will work but you may have some filling left over) and gently crush with your hands until you have a mix of dime-size pieces, small crumbs, and everything in between. Add peanuts, brown sugar, and salt and toss to combine. Drizzle in butter and toss to evenly coat. Using your hands and the bottom of a measuring cup, press firmly and evenly into bottom and up sides of dish. (Mixture will look and feel crumbly, but it will hold together when baked.) Bake crust until a shade darker, 20–25 minutes. Let cool.

Do ahead: Crust can be baked 3 days ahead. Store tightly wrapped at room temperature, or freeze up to 1 month.

Pour water into a medium saucepan to come 1½" up the sides and bring to a bare simmer over medium-low heat. Whisk eggs, brown sugar, and salt in a large heatproof bowl just to combine (or use the bowl of a stand mixer if you’ve got one). Set over saucepan (bowl should not touch water) and heat egg mixture, stirring constantly with a heatproof rubber spatula, until sugar dissolves, about 4 minutes (mixture will no longer feel gritty when rubbed between your fingers). If you are concerned about undercooked eggs, heat mixture longer, still stirring constantly, until an instant-read thermometer registers 165°, about 3 minutes more. Remove bowl from heat and add vanilla to egg mixture. Using an electric mixer, beat on high speed until thick and pale and doubled in volume, about 10 minutes. (Or, if using a stand mixer, beat with the whisk attachment, 6–8 minutes.)

Using spatula, mix peanut butter in another large bowl to loosen up and smooth out. Stir one third of egg mixture into peanut butter to lighten, then gently fold in half of remaining egg mixture, running spatula down sides and along bottom of bowl, then lifting up through center and over top while rotating bowl, until just combined. Repeat with remaining egg mixture (it will lose a lot of volume, and that’s okay).

Starting on low speed and gradually increasing to medium-high, beat cream in the same bowl you used for egg mixture (no need to wash) until soft peaks form, about 2 minutes. Gently fold into peanut butter mixture and scrape into crust. Dollop jelly all over; swirl with a butter knife. (For more defined swirls, freeze pie 30 minutes before adding jelly.) Freeze at least 8 hours before serving.

To slice, run a chef’s knife under hot water to warm up the blade, then wipe to clean and dry between slices. Use an offset spatula or fork to loosen slices from dish. If pie is frozen very hard, you may need to let it temper in the fridge 30 minutes before serving.

Do ahead: Pie can be made 2 weeks ahead. Wrap tightly and freeze.

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