When I was cooking at the Seafarer's Inn back in the early '70's turtle soup was very popular. I learned to make it there and my husband loved it. Sea turtle meat is now out-lawed so I found this mock turtle soup recipe and surprised him. He could barely tell the difference.
Brown onion in the butter and oil, add the oxtails and brown slightly. Add the spices and herbs, then stir in the flour until it bubbles, adding more butter and oil as needed.
Pour in the hot water and stock and bring to a boil. Add the remaining ingredients, except the egg, parsley and sherry. Simmer for 2 hours. Remove the oxtail, cut the meat and marrow away--add back to the soup and discard the bones.
When ready to serve, chop the eggs coarsely and stir into the soup. Ladle into bowls, stir in a teaspoon of sherry to each, top with parsley...and put a cruet of sherry on the table, for atmosphere if nothing else.