Add all the ingredients to a jar / glass big enough for an immersion blender*
Blend, then taste and adjust for seasoning. Refrigerate for 4 hours - overnight to firm up.
Use in sandwiches, dips, dressings, any where you would use regular mayo!
*Food Processor / Blender
If using a regular blender or food processor, add all ingredients except the oil (if using) and blend until smooth. Slowly add in oil and blend until emulsified.
Notes
Black Salt (Kala Namak) - You can also add a dash of Black Salt for a little eggy flavor if you like. I tried it out and found it a bit much, so it's not for me, but you do it if you like!