Pour the cold heavy whipping cream into a large mixing bowl. Using a hand mixer or stand mixer fitted with the whisk attachment, beat the cream on medium-high speed until stiff peaks form. This will take about 2-3 minutes. The cream should be thick and hold its shape when you lift the beaters.
In a separate medium bowl, add sweetened condensed milk, vanilla extract, and kosher salt. Whisk together until fully combined and smooth.
Gently fold the sweetened condensed milk mixture into the whipped cream using a silicone spatula. Use slow, folding motions to avoid deflating the cream. Keep folding until no streaks remain and the mixture is smooth and fluffy.
Pour the ice cream base into a loaf pan or freezer-safe container. Smooth the top with a spatula. If you want to add any mix-ins (like chopped cookies, fudge swirls, or fruit), this is the time to gently fold them in or layer them on top.
Press a piece of plastic wrap or parchment paper directly onto the surface of the ice cream to prevent ice crystals from forming.
Freeze for at least 6 hours, or overnight, until completely firm.
Let the ice cream rest at room temperature for 5-10 minutes before scooping for the creamiest texture.