In a glass jar (see notes), pour in the avocado oil. Add egg to the oil and let the ingredients settle for 1 minute.
Take the immersion blender and let it touch the bottom of the container, piercing the egg yolk completely.
Turn the immersion blender on and leave it on the bottom for about 20-30 seconds, until the whole bottom has turned white in color.
VERY SLOWLY lift it up to continue emulsifying. This process should take anywhere between 30 seconds to 1 minute. Continue blending until the mixture has thickened to your desired amount.
Add mustard and water to the mixture.
Stir in the salt and gently fold in the lemon juice. Store in an airtight container in the refrigerator for up to 7 days.
