Halve avocados, remove pit and scoop flesh out of hulls. Discard hulls. Cut flesh into small cubes.
Heat broth to boil. Reduce heat to simmer. Add Sherry and half the avocado.
Combine remaining avocado with creme fraiche and eggyolk in food processor or blender and liquefy/zip till creamy. Add to soup, which will thicken. Soup MAY NOT BOIL AGAIN or it will become extremely bitter.
Season with Cayenne pepper and chopped dill.
Serve with large, freshly-toasted croutons, a dusting of paprika and a small dollop of creme fraiche on every plate. Another interesting topping is deep-fried tortilla strips - be creative. Just remember - DO NOT BRING THIS TO A BOIL once you have put the avocado in or it will be horrifically bitter!