Place the cashews in a medium bowl and cover them completely with water. Allow the cashews to soak for a few hours, or up to overnight.
Drain the soaking water from the cashews.
If making a larger batch of cashew milk, place the entire cup of soaked cashews into a blender. If making just half the batch of cashew milk and freezing the other half of soaked cashews for a future batch of cashew milk, then place half the soaked cashews into a blender, place the other half into a freezer safe container and place in the freezer to use later (this way you've already got some cashews soaked and ready to go!).
Add water to the blender. If using the whole cup of soaked cashews, add 3 cups of water to the blender. If only using half, add 1 1/2 cups of water to the blender.
Blend on high (work your way up to high on your blender's settings) until the cashew milk is smooth and creamy, which should take just a couple of minutes.
Store cashew milk in a mason jar with a lid in the refrigerator, and use within 5 or 6 days.