Pour the heavy cream and vanilla extract into a large mixing bowl or the bowl of a stand mixer. On medium-high speed, whip the cream until it holds stiff peaks, about 3 minutes (less if you’re using a stand mixer).
Add sweetened condensed milk to whipped cream. Fold together until just combined and silky and smooth. A few small lumps may remain, it’s important not to over mix as that will deflate the mixture.
Spread into a 8 or 9-inch loaf pan. Cover with foil and freeze for one hour.
Take pan out of the freezer and stir to mix in frozen portions. Put spoonfuls of room temperature hot fudge on top, and then gently swirl in hot fudge, using a table knife.. Don’t over mix, you want to see swirls of hot fudge.
Cover pan tightly with foil. Freeze for at least 6 hours or until firm.
The hot fudge sauce should be at room temperature. Make homemade hot fudge or use store bought hot fudge topping.
Create your own signature ice cream. Here's some ideas: Crush a handful of Oreo cookies and swirl them into the partially frozen ice cream. Swirl in caramel topping and a handful of peanuts. Try strawberry, blueberry, or cherry jam swirls.
For longer storage: Line the loaf pan with parchment paper before freezing the ice cream. When it’s frozen, lift the ice cream out of the pan with the parchment paper and transfer it to a resealable container. Put a layer of plastic wrap or parchment directly on top of the ice cream to prevent ice crystals.