Before you start to mix this up, be sure you've pre-frozen the ice cream canister that goes with your ice cream maker; if you don't, your ice cream won't freeze.
In a large mixing bowl, combine the whole milk and sugar 'til the sugar dissolves, about 1-2 minutes.
Whisk in the heavy cream, vanilla extract, and sea salt.
Turn on the ice cream freezer, and pour the mixture into the freezer bowl with the churn paddle in place.
Then place the cover on top, and let it mix 'til it thickens, about 20-25 minutes.
About 5 minutes before the mixing is completed, add the crushed Butterfinger bars through the top of the ice cream maker, and let the candy mix in completely.
Once the candy is all mixed in, turn off the machine, and scoop the soft-serve ice cream into bowls for serving; or if desired, scoop it into an airtight container, and place it in the freezer for 2-3 hours to firm up more. Then serve when ready.
Notes
*I recommend freezing the crushed Butterfinger Bars ahead of time, so they don't warm and melt the ice cream when you add them.