To soak the cashews, place them in a bowl and cover with hot (but not boiling) water. Leave for at least 4 hours (or ideally over night).
Drain and discard the liquid (don't use this to make the milk). Rinse the cashews, then throw them in the blender together with 3 cups of water and 1 tbsp of maple syrup. Blast on highest speed for about 60 seconds, or until smooth and creamy.
Strain the milk through a fine mesh strainer, tea towel or a cheesecloth into a container and store in the fridge for up to 3 days.