Melt the sugar in a heavy saucepan over medium heat, stirring gently, until deep amber, about 5 to 7 minutes.

Off the heat, whisk in the butter, then slowly pour in the room temperature cream. Stir in the salt and let cool to room temperature.

Beat the cold heavy cream to stiff peaks in a large bowl.

Fold the condensed milk and vanilla into the whipped cream until no streaks remain.

Layer a third of the cream mixture and a third of the caramel in a 9x5 inch loaf pan, repeat twice, ending with caramel. Swirl gently with a knife.

Cover and freeze until firm, at least 6 hours.

Let soften 5 to 10 minutes, then scoop and serve with extra salt if desired.