Rinse the cashews a few times, then place in a mason jar, cover with 2–3 cups of filtered water.
Let soak for several hours or overnight in the refrigerator, changing the water once or twice.
Discard the soaking water and rinse the cashews a few times. Wash the jar for use as the milk container.
Place the cashews in the blender and add a small amount of the filtered water and blend.
Scrape down the sides and add a little more water, and blend until smooth.
Keep adding more and more of the water, blending in between, until all the water is added and the consistency is smooth.
For a smoother consistency, strain into the mason jar using a cheesecloth or fine sieve, then strain back into the blender, then strain one more time into the mason jar.