Whisk sweetened condensed milk and avocado in a medium mixing bowl. Set aside.
In a separate bowl, whip the heavy cream until stiff, forming whipped cream.
Fold the avocado mixture into the whipped cream mixture until combined.
Pour mixture into loaf pan and freeze at least 4 hours.
Notes
Put your loaf pan in the freezer while you're prepping the ice cream so that you're pouring the mixture into a cold pan. A metal pan is ideal, but ensure the pan that you use is freezer-safe.