Meat from one snapper turtle, cut in small pieces. Have knuckles broken into 2 inch pieces. Place knuckles in a roasting pan and add the butter or chicken fat, onions, celery, carrots, thyme, marjoram, cloves, bay leaf, salt and pepper. Bake at 400-F until brown. Remove from oven and add flour, mixing well and cook 30 minutes longer. Pour browned mixture into a large soup kettle, add the broth and tomatoes, and cook slowly for 3-1/2 hours. Combine the snapper meat with 1 cup sherry, some salt, the tabasco and lemon slices, and simmer for 10 minutes. Strain the soup and combine the two mixtures. Add the chopped egg and the balance of the sherry and serve immediately.