Using a stick blender, hold it to the bottom of the container and pulse it off and on until you see the mayonnaise start to form, then you can start to move the blender a bit more until the mayonnaise is nice and thick.

If using a regular blender, place first 4 ingredients and 1/4 cup oil in the blender and blend on low. While the machine is blending, SLOWLY pour in another 1/2 cup oil. You may have to stop and scrape down the mayo. Add the lemon juice, vinegar and the remaining 1/2 cup oil.