I found this recipe in an old James Beard cookbook over 25 years ago. People beg me to make it. It's simple and easy and...addictive! Make this appetizer right before serving. To preserve any leftover guac, store it in a container with a minimum of surface area exposed. Smooth out the top of the guac and put plastic wrap directly onto it to minimize oxidation (the browning of the guac). Seal the container tightly.