Cook whole bacon strips slowly over low heat in a large soup pot until almost all fat is rendered out, or omit bacon and melt butter. Add diced onion, salt and pepper and cook, stirring occasionally, until soft, about 5 minutes. Add chicken stock, bay leaves and potato and simmer 20 minutes or until potato slices are soft. Meanwhile, finely chop chayote in a food processor.
Remove and discard bay leaves and bacon and add chopped chayote. Bring to a boil, return to a simmer, and cook, uncovered, until the chayote is soft, about 15 minutes.
Puree in a blender until smooth. Strain back into pot, pressing with a ladle to extract all juices. Add cream or half and half. Bring to a boil and remove from heat. Serve immediately with lime wedges.
c.1997, M.S. Milliken & S. Feniger, all rights reserved