Add half of the black sesame seeds and half of the white sesame seeds to a non-stick skillet and spread them into an even layer. Toast the seeds over medium heat, stirring regularly, until the white sesame seeds are golden brown, 5-8 minutes. Transfer the toasted sesame seeds to a blender and toast the other half of the seeds.
Let the seeds cool down for about 15 minutes. Next, add the drained soaked cashews and water to the blender. Blend on high speed for about 1 minute.
Using a nut milk bag, strain the cashew sesame milk. You can keep the pulp to add to baked goods, oatmeal, etc.
Transfer the cashew sesame milk to a medium saucepan. Add the maple syrup (or white sugar) and salt. Bring to a simmer over medium heat and simmer for about 10 minutes, whisking regularly. The milk should turn from a light grey color to a deep dark.
Enjoy warm during the colder months, or chilled with ice in the summer! Black sesame cashew milk will keep for up to 5 days in the refrigerator. It will separate. This is normal. Just give it a good stir or shake before using.