In a food processor or blender, combine the egg, mustard, lemon juice, salt, and cayenne, and process on high speed until smooth. With the machine running, slowly add the oil in a steady stream until an emulsion forms. Adjust seasoning, to taste. Place the mayonnaise in a mixing bowl and fold in the chopped herbs. Cover and refrigerate for 2 hours before serving.
*RAW EGG WARNING
The American Egg Board states: "There have been warnings against consuming raw or lightly cooked eggs on the grounds that the egg may be contaminated with Salmonella, a bacteria responsible for a type of foodborne illness.… Healthy people need to remember that there is a very small risk and treat eggs and other raw animal foods accordingly. Use only properly refrigerated, clean, sound-shelled, fresh, grade AA or A eggs. Avoid mixing yolks and whites with the shell…"
Yield: about 1 1/2 cups