1. Pre-heat your oven to 350. Combine the graham crackers, brown sugar, and salt into the bowl of a food processer. Pulse till you have a fine, sandy consistency, with no large chunks of cracker. Transfer the crumbles to a bowl and add the melted butter, mixing till evenly distributed. Add the crumble to a pie pan and press to form the crust, about 1/8th inch thick. Bake till fragrant, about 8-10 minutes.
2. While the crust is cooling, add the heavy cream to the bowl of a stand mixer. With the whisk attachment, whip on medium-high until medium stiff peaks form. Reduce to low speed and add the powdered sugar. Return to medium-high and whip for about a minute more. Using a rubber spatula, transfer the whipped cream to a separate bowl. 
3. Add the cream cheese, salt, and vanilla extract to the stand mixer bowl. Using the paddle attachment, beat the cream cheese mixture at medium-high till light and airy, about a minute. Reduce the mixer to medium low, and slowly add the full jar of peanut butter. Increase the speed and beat till combined. With the mixer on low speed add about 1/3 of the whipped cream at a time, stirring till just combined before adding next addition.
4. Drizzle about half the jar of fudge sauce around the base of the cooled pie crust. Add the peanut butter filling over top. Cover with plastic film and transfer the pie to the cooler and chill for at least an hour (this can be made the night before and stay in the fridge till ready to serve). When ready, remove the plastic film and drizzle with the remaining fudge sauce. Slice and serve!