Boil the kettle and place the cashews in a heatproof bowl. Cover them with boiling water and set aside for at least 10 minutes (longer if it suits).
Drain the cashews and place them in a high speed food processor along with the 200g water. Blitz to create a smooth and creamy cashew base.
Place the cocoa in a medium saucepan and pour over the 75g boiling water. Mix to combine and bloom the cocoa - it should be a thin paste consistency.
Sprinkle the caster sugar in a heap and sprinkle the xanthan gum on top of that. Mix quickly so that both ingredients dissolve into the cocoa mixture. Add the cashew milk, glucose syrup or light corn syrup and salt.
Place the mixture over a medium heat and cook for 1-2 minutes or just until the sugars have completely dissolved and the mixture is an even chocolate brown colour. Allow the mixture to cool a little before pouring it into your 470ml tub. It should come up to the fill-line or just under.
Place in the freezer for 16-24 hours with the lid off. Leaving the lid off during freezing helps minimise the risk of your mixture developing a hump which can damage your machine.
When you are ready to eat, process your mixture on ice cream. I like to re-spin this recipe once. Return any leftovers to the freezer with the lid on.
Notes
You might be able to push the sugar a little bit higher if you like a sweet ice cream. I wouldn't personally go further than 90g. If you add too much sugar, your ice cream won't freezer properly.
Glucose syrup is more commonly available in the baking aisle in Australia and the UK. Light corn syrup is more commonly available in USA and Canada. Choose light (light refers to colour and flavour) and a brand without high fructose corn syrup. I tested Karo brand.
If your mixture comes up to under the fill-line, you can always add water to reach it (but make sure you stir thoroughly).
I do not have a substitute for cashews at the moment but I am working on a Ninja Creami macadamia ice cream recipe.