Place 1/4 cup olive oil, the egg, mustard and salt together in a blender or food processor and mix thoroughly.
While the blender or processor is running, very slowly drizzle in the remaining 1 cup of oil - the slower you add the oil, the thicker and creamier the emulsion will be.
After all the oil has been added and the mixture has emulsified, add the lemon juice and blend on low to incorporate.
Recipe Notes
- Make sure all ingredients are at room temperature prior to making this mayonnaise. - If using a food processor, make sure there is the ability to drizzle in oil while the processor is running.