Margarita Jameson’s Cold Avocado Soup

This soup was served on a visit to friends of my mother and stepfather. Margarita and Juan Jameson, both of old Mexican familias de abolengo (blueblood families), welcomed us in their beautiful apartment in the hills of Mexico City with a marvelous comida consisting of cold avocado soup, pan-fried chicken breasts, sweet-and-sour marinated ancho chiles (see Chiles Anchos Nana Luz), and olive-size new potatoes in a tomatillo sauce. A sim