Add all the ingredients to a blender and puree until smooth. If you think the mixture is too thick, add the extra 1/2 cup heavy cream and stir it in by hand.
Transfer the mixture to a freezer-safe container and chill for 4 hours.
After 4 hours, process the mixture in an ice cream machine for about 20 minutes or until it sets.
Serve immediately for soft serve or bring it back to the freezer for a few more hours for a firmer texture.
Notes
If you don't have an ice cream machine, just freeze the ice cream for 6 hours and serve.