Soak your raw cashews in water for at least 2-4 hours, or a quick soak in hot water for about 30 minutes if short on time.
Once the cashews are soaked and softened, drain and rinse them under cold water. Gather the other ingredients: water, lemon juice, garlic, Dijon mustard, salt, and kala namak.
In a high-speed blender, combine the soaked cashews, water, lemon juice, garlic, Dijon mustard, salt, and kala namak. Blend on high until completely smooth and creamy.
Add your choice of fresh herbs to the blender and blend again until the herbs are finely incorporated and the aioli is a lovely green color.
Taste the aioli and adjust the seasoning if necessary, adding more lemon juice or garlic as desired.
Transfer the aioli to a storage container and refrigerate for at least 30 minutes to allow the flavors to meld. Serve chilled.