Combine all of the ingredients in a high-powered blender and blend until smooth. (If you don't have a high-powered blender, you may need to pour the milk through a cheesecloth or nut bag before serving).
Refrigerate the milk in a covered bottle for up to 3 days. Just give it a little shake before using.
To soak the cashews, place them in a bowl and cover with filtered water. Let them sit for at least 4 hours, then drain and rinse.