In a high, narrow container, pour oil.
You can take any oils that you like, but not go too far with concentrated flavors.
Add salt and mustard.
Add peeled egg in oil.
Dip the blender to the mix, egg should be inside.
Turn it to high speed.
Pressing the a blender to the bottom,
until mass became homogeneous.
At this stage, add vinegar.
Beat little bit more.
If you like a very thick mayonnaise, it's ready.
But if you prefer more soft, then add couple tablespoons of hot water in the end.