In a small bowl, combine mayonnaise, black truffle oil, lemon juice, garlic, chopped parsley, MSG, and black pepper.
Mix until smooth and then top with more parsley to garnish.
Notes
Not all truffle oils are created equally! Some may be more flavorful than others, so I recommend starting with ½ the amount this recipe calls for and then adding in more to taste until you find the right balance.
I sometimes like to add fresh lemon zest to my aioli to add a little more flavor and texture.
Keep this aioli in the fridge for up to two weeks, but don't try to freeze it.