The Accidental Locavore never buys mayonnaise anymore because it's so easy to make, and once you've had homemade mayo, you're spoiled for life. My dad taught me a long time ago how to make mayonnaise, so here is his no-fail recipe.
In the bowl of a food processor (blender, or stick blender will work) add the egg, lemon juice, olive oil, Dijon mustard, salt, garlic, and herbs. Process a few times until well mixed. With the motor running, very slowly pour in about a cup of oil. My father uses ¼ cup olive oil and the rest canola. As you keep pouring you will see it start to emulsify and look like mayonnaise, when it’s your desired texture, stop, and taste. Correct seasonings and you’re done.