Place your cashews in an extra large glass jar (needs to be glass, according to the internet) along with all the ingredients for the milk. Leave them to soak for a minimum of 4 hours, or overnight, if possible. Make sure you cover them and put them in the fridge if you're going the overnight route - I have left them on my kitchen counter in hot weather, and woke up to very soured cashews. Not ideal. Defeats the purpose of this anti-waste recipe, etc.
Once soaked, place the mixture into the blender, and blend for 2 minutes or so. You might have to divide the mixture into two batches for blending purposes.
Pour the milk through a nut milk bag (available at health and bulk food stores in Australia) and store in a glass container, with a lid, in the fridge. You need to use the milk relatively quickly (2-3 days) because there are no preservatives. As I mentioned, you'll be able to tell verrrrry quickly when your milk is past it's prime.
Notes
(This ratio is applicable to most nuts I've tried, namely almond)