Open the melon and scoop out all the flesh you can get, discard the seeds. Blend all of it for at least 30 seconds, until it is a very smooth liquid.
In a 2 liter large container with lid, add the heavy cream, milk and corn syrup. Mix them together until they are all incorporated, and add the blended melon, once again mixing until the mixture is smooth.
To add the xantham gun, first start stirring your mixture to create movement, and very slowly whisk the xantham gum into the mixture, stirring it all along. The gum can act very quickly so do NOT put it all at once.
Close the container and store it in the fridge until the mixture’s temperature is at least 45F or 7C, which is probably around 6 or more hours depending on the fridge. You can also do an ice bath to cool ths mixture faster but its recommended to let it sit for a while anyway.
When ready, start your ice cream machine as per the machine’s instructions and pour the mixture in. Let it run for the recommended time or until you are happy with the consistency, put the ice cream into a bowl and freeze it ideally for at least 4 hours before serving.