Add the aquafaba, mustard, honey, salt, and apple cider vinegar to a wide mouth jar.
Insert the immersion blender and blend on high speed for 30 seconds. The mixture should turn white and frothy.
Gradually add the avocado oil with the blender still running. Continue blending for another minute or two until the mayo thickens. Don't worry if it's not as thick as regular mayo yet.
The mayo can be used right away if needed, but it will thicken up more after a couple hours in the refrigerator.