Whisk together the condensed milk, vanilla and salt in a large bowl; set aside.
14 ounce can sweetened condensed milk, 2 teaspoons pure vanilla extract or vanilla bean paste, Pinch table salt
Whip the cream with a mixer on medium-high speed until firm peaks form, about 2 minutes.
2 cups cold heavy cream
Fold about 1 cup of the whipped cream into the condensed milk mixture with a rubber spatula until combined, then fold that mixture into the whipped cream until well blended.
Pour into a chilled 9-by-5-by-3-inch metal loaf pan, and freeze, covered, until thick and creamy, like soft-serve, about 2 hours.
Stir in any desired mix-ins with a spoon.
Continue to freeze, covered, until solid and scoopable, about 3 hours more.
Notes
Sweetened condensed milk: I recommend using full-fat condensed milk for creamier ice cream. However, you can use reduced-fat if you prefer.
Salt: The pinch of salt just helps to balance out the flavor of the ice cream, but it doesn't make it salty.
Cream: It's important to use heavy cream so that it whips up properly.