In a bowl, add the nuts along with enough water to cover them by 2” or so. Cover, place in the refrigerator, and let them soak at least 12 hours (I typically let them go 48 hours. The longer they soak, the smoother the milk will be)
Drain nuts and discard the soaking liquid.
To the bowl of a food processor (or blender) add the soaked nuts, sweetener (if using), hot water, and blend until very smooth (~ 2 minutes)
Over a medium-size bowl, strain the mix through a nut bag, pressing down on solids. (see notes about drying the solids)
The milk will keep in the refrigerator a week.