In a large bowl, use a hand or stand mixer to beat the cold heavy cream on medium-high until stiff peaks form, about 2–3 minutes. Try not to overbeat, as you want it fluffy but still smooth.
In another bowl, whisk together the sweetened condensed milk, ½ cup dulce de leche, vanilla, and salt until completely smooth. The mixture should look glossy and caramel-colored.
Use a rubber spatula to gently fold the whipped cream into the dulce de leche mixture. Take your time with this part, as you don’t want to lose all that fluffy whipped volume. Also, try to make sure the dulce de leche is evenly distributed, or you’ll have white patches of plain whipped cream throughout your ice cream.
Fold in the chopped Oreos, saving a small handful for sprinkling on top later. You can also use holiday Oreos for an extra festive touch!
Pour half the mixture into a 9×5-inch loaf pan or freezer-safe container. Add spoonfuls of dulce de leche and swirl with a knife or skewer (If you can, quickly heat the dulce de leche in the microwave for only 5-ish seconds to make it more spreadable).
Add the remaining ice cream mixture and repeat with more dulce de leche swirls. Sprinkle the reserved Oreos on top.
Cover tightly with foil or plastic wrap and freeze for at least 6 hours or overnight, until firm enough to scoop. When you’re ready to serve, let it sit at room temperature for about 5 minutes to soften slightly.