Beat the cold heavy cream on medium-high speed until it holds stiff peaks and is thick enough to hold a swirl.
Make the Pumpkin Base
In another bowl, whisk the sweetened condensed milk, pumpkin puree, pumpkin pie spice, vanilla, and salt until smooth. Blot the pumpkin with a paper towel first if it looks watery.
Fold and Freeze
Gently fold the whipped cream into the pumpkin base in three additions, keeping it airy.
Scrape into a loaf pan, press plastic wrap onto the surface, cover, and freeze at least 6 hours or overnight.
Notes
Without condensed milk: Whip 1 cup powdered sugar into the cream, then fold in the pumpkin and spice.
Keep it creamy: Start with cold cream and blot excess moisture from the pumpkin to avoid an icy texture.
Serving: Let it soften on the counter for 5 to 10 minutes before scooping.