Step 1: Place a large mixing bowl and your whisk or beaters in the freezer for 15 minutes to chill.
Step 2: In a medium bowl, stir together the chilled sweetened condensed milk, vanilla extract, and salt until well combined.
Step 3: In the chilled large bowl, whip the heavy cream on medium-high speed until stiff peaks form (be careful not to overbeat into butter).
Step 4: Using a rubber spatula, gently fold about half a cup of the whipped cream into the condensed milk mixture to lighten it.
Step 5: Carefully fold the lightened milk mixture back into the remaining whipped cream until just combined and no white streaks remain.
Step 6: Transfer the mixture into a 9x5 inch loaf pan or an airtight glass container.
Step 7: Cover tightly with plastic wrap or a lid and freeze for at least 6 hours, or preferably overnight, until firm.