Heat the cream in a microwave-safe bowl until hot.
Whisk in the chopped Butterfingers, cocoa powder, and peanut butter powder. Not everything will melt smoothly, but that's okay.
Transfer the cream mixture to your blender and blend until smooth, about 30 seconds.
Refrigerate until cold, at least 4 hours.
Add the chilled cream mixture (it will be very thick) to your mixer bowl (or to a large bowl if using a hand mixer), and whip until lighter in color, about 45 seconds or so. Scrape the bowl.
Whisk together the sweetened condensed milk and milk until well-combined and add to your mixing bowl.
Whisk on medium-low speed to combine. Scrape bowl as necessary.
Heat the peanut butter for a few seconds so it is easy to drizzle.
Layer 1/3 of the ice cream base into a freezer-safe container.
Sprinkle on 1/3 of the second amount of chopped Butterfingers and drizzle on 1/3 of the peanut butter.
Repeat twice more, finishing with the mix-ins.
Press plastic wrap directly on top of the ice cream and freeze until firm, 8 hours or overnight.
Enjoy within 10 days to 2 weeks.
Notes
To Use Full-Size Bars
Melt 4-5 full-sized Butterfinger bars into the base in place of the 15 fun-sized bars. Chop 2 full-sized bars to use for layering.
Storing
Keep in the freezer with plastic wrap pressed directly on top of the ice cream for up to 2 weeks. It really is best within the first week, though. After that, flavor and texture will suffer.