Add all the ingredients but the black salt to an immersion blender cup. Blend with an immersion blender until smooth and emulsified. Alternatively you can use a regular blender. But slowly stream in the oil as the blender runs to create the emulsion.

Add the sauce to a saucepan and gently heat over medium low until the cornstarch is activated and thickens the sauce. Remove from heat and add in the black salt. Taste and adjust for seasoning. If your emulsion breaks you can simply blend it up again.

Enjoy immediately!