Gather ingredients: 2 cups heavy cream (or half-and-half), 1/2 cup sugar, 1 teaspoon vanilla extract, pinch of salt
Add-ins (optional): 1/2 to 1 cup crushed cookies, chocolate chips, fruit, or caramel sauce
Prepare the ice bath: fill a large bowl or bucket with ice
Add salt to the ice: about 1 cup salt per 1 bag ice (enough to make the ice very salty)
In a small bag (sealable), combine cream, sugar, vanilla, and salt (pinch)
Seal the small bag tightly, removing as much air as possible
Place the small bag inside a larger bag (sealable) for double-bag protection
Seal the large bag tightly
Put the bag(s) into the ice bath
Shake and massage continuously for 10–20 minutes (until thickened)
Check texture: it should look like soft-serve when done
Carefully remove the bag from the ice
Wipe off excess salt and open the small bag
Stir in any add-ins (if not already mixed)
Serve immediately as soft-serve, or transfer to a container and freeze 1–2 hours for firmer ice cream