In a saucepan over medium heat, add your butter and brown sugar. Cook until the butter has melted and the sugar is dissolved and starting to bubble up, about 3-4 minutes.
Pour mixture in to a bowl, and whisk in your butterscotch. Cover your bowl with plastic wrap, making sure to have the plastic wrap touching the surface of the ice cream base so it does not get a skin. Refrigerate for at least 3 hours.
Spoon your ice cream into a shallow container or a loaf pan. Press plastic wrap the surface of the ice cream. Freeze for at least 4 hours, or until solid.