For the Stock: Combine all the ingredients in a large stock pot, bring the stock to a boil and simmer it, partially covered for two to three hours. (It tastes better the longer it simmers, as long as you don't cook away the liquid.) Strain the stock and cool in order to skim off the fat.
Remove all of the meat from the bones and refrigerate for adding to the soup later. Discard other vegetables, bones, turkey skin, etc.
For the Soup: In a large stockpot, sauté the onion and garlic in oil until soft. Add the carrots and celery and mushrooms and cook the vegetables for an additional 5 minutes . Stir occasionally.
Add the flour and stir for one minute.
Add the stock, marjoram, salt and pepper, and barley or rice. Bring the soup to a boil, reduce heat, partially cover the pot, and simmer the soup for about 1 hour. Add the turkey meat and hot pepper sauce. Adjust seasonings, and heat the soup to boiling. Sprinkle the soup with parsley just before serving.