In a large soup pot over low heat, fry the bacon until almost all the fat is rendered, or melt the butter. Raise the heat to medium, add the onion, salt and pepper and cook, stirring occasionally, until soft, about 5 minutes. Add the stock or water, bay leaves and potato and simmer until the potato slices are soft, about 20 minutes
When the potato slices are soft, remove and discard the bay leaves and bacon. Add the chayotes and bring to a boil. Return the heat to medium and simmer, uncovered, until the chayotes are soft, about 15 minutes. Remove from the heat and let cool slightly. Working in batches, puree the soup in a blender until smooth. As each batch is pureed, pour the puree through a sieve placed over a bowl, pressing with the back of a spoon to extract all the juices. Pour the puree back into the pot, add the cream or half-and-half and bring just to a boil. Taste and adjust the seasonings.
Remove from the heat and ladle into warmed bowls. Slip a few lime slices into each bowl and serve hot.
c.1997, M.S. Milliken & S. Feniger, all rights reserved