Place the macadamia nuts in a sealable container large enough to hold them and cover with water. Seal and refrigerate for 12 hours.
After 12 hours, drain and rinse the soaked nuts.
Place them in a high-speed blender with 4 cups / 950 ml of fresh water and the salt.
Blend on high for 1 to 2 minutes, until the nuts are completely pulverized and the mixture is smooth.
To strain, place a fine-mesh strainer or a nut milk bag over a large bowl. Slowly pour the blended mixture through, allowing the milk to collect in the bowl. Gently press the pulp with a spoon or squeeze the bag to extract all the liquid.
For optional add-ins, pour the strained milk back into the clean blender.
Add the MCT oil powder and/or vanilla and blend on low for just 10 seconds to combine.
Transfer the finished macadamia nut milk to a 1-quart / 950-ml or larger airtight container and store in the refrigerator.
Don't discard the leftover nut pulp! Dehydrate it to make macadamia flour for baking or add it to smoothies for extra fiber.