Preheat oven to 325 degrees F. Grease the sides only of a 9-inch springform pan (don’t grease pie plate if using).
Add the Oreos and butter to a food processor and process until finely ground (or crush with a rolling pin then mix with butter in a bowl).
Pour the crumbs into the springform pan or pie plate and use the bottom of a measuring cup or glass to firmly press the crumbs into the bottom. If using a pie plate, also press the crumbs up the sides.
Bake at 325 for 10 to 12 minutes. Transfer to a wire rack and cool completely.
Add the unflavored gelatin to a microwave safe bowl then pour the cold water over top; let stand for 5 minutes. Microwave for 10 seconds. Stir the mixture, then set aside. Immediately proceed with the next step.
Add 1 cup heavy cream and vanilla extract to a medium mixing bowl. Whip using an electric hand mixer until soft peaks form (the whipped cream folds over when you lift the beaters out of the bowl).
Turn the mixer to low and slowly pour in the gelatin mixture. Mix until well combined then increase the speed to medium and continue mixing until stiff peaks form (the whipped cream stands straight up and doesn’t fold over when you lift the beaters out of the bowl).
In a separate large mixing bowl, using the same beaters (no need to clean), beat the cream cheese, powdered sugar and peanut butter on medium-low until combined. Increase speed to medium-high and beat until light and fluffy, about 2 minutes.
Add the whipped cream and the Butterfingers to the peanut butter mixture and fold until evenly combined.
Pour the mixture into the prepared pan and freeze while you make the ganache.
Add the heavy cream and corn syrup to a large microwave safe bowl. Microwave until just boiling, about 2 minutes. Remove from microwave and add chopped chocolate. Let stand 3 minutes, then whisk vigorously until ganache is melted and smooth.
Let the ganache cool to warm, then pour it over the top of the pie and spread it to edges. Sprinkle the top with desired amount of crushed Butterfingers.
Cover and chill the pie in the refrigerator for at least 5 hours before serving (then slice and serve immediately because it will soften) or freeze for at least 2 hours. If frozen, let the pie sit at room temperature for 20 minutes or so to soften up a bit before serving.
Use a hot knife to slice the pie for the cleanest slices. You can either run the knife under hot water or fill a large glass with hot water, then dip the knife in the hot water before each cut. Wipe the knife clean with a paper towel after each cut, then repeat.
