Preheat oven to 350°.
Using a food processor or blender, crush the Oreos into fine crumbs.
Mix the melted butter, sugar, and Oreo crumbs together in a mixing bowl.
Press the Oreo crumb mixture into the bottom of an 8-inch springform cheesecake pan and up the sides.
Add the cream cheese and sugar to a large mixing bowl. Use an electric mixer to whip them together until fluffy.
To the cream cheese mixture, add the eggs, vanilla extract, sour cream, and flour. Mix until well combined.
Pour half of the cheesecake mixture over the crust in the cheesecake pan.
Warm up half the hot fudge sauce in a microwave-safe bowl for 30 seconds or until pourable. Pour the hot fudge onto the cheesecake layer. You can swirl it around a bit if you like.
Chop 3 mini Butterfingers and 3 Reese's Peanut Butter cups. Sprinkle the chopped candy bars over the hot fudge layer.
Pour the rest of the cheesecake batter into the pan and smooth out the top.
Bake the cheesecake for 50-60 minutes. The center should be very slightly jiggly.
Cool the cheesecake on the counter and then refrigerate the cheesecake for 4 hours or overnight.
ADD THE TOPPINGS: Spread the remaining hot fudge sauce and pour it over the top of the cheesecake. It may be helpful to warm the hot fudge a little bit so that it spreads more easily on the top. Chop the remaining Butterfingers and Reese's Peanut Butter cups and sprinkle over the top of the cheesecake.
MAKE THE FROSTING: Use an electric mixer to whip the peanut butter, cream cheese, and butter together.
Add the powdered sugar and beat until well combined.
Add the frosting to a piping bag or ziplock bag with the corner snipped off.
Pipe dollops of the peanut butter frosting around the edge of the cheesecake. Refrigerate the cheesecake until ready to serve, or slice and serve the cheesecake immediately.