In a large soup pot over high heat, brown the oxtails or beef bones until rather dark. Add a gallon of water, the marjoram and the bay leaves. Bring to a boil, lower to a simmer, and cook for two hours (or longer if possible). Strain the stock and set aside. (You can do this a day or two ahead, and refrigerate the stock, which will congeal.)
Slice open the peppers and remove all seeds and membranes. Slice the onions and peppers as thin as possible.
In a large heavy pot over medium-high heat, heat the olive oil until it shimmers, then add all the onions except the chives and the garlic. Cook, stirring every two minutes or so, until the onions have browned rather darkly. This will take as much as a half-hour, but is essential to getting the sweetness of the onions. Then add the garlic and the peppers.
Add the port or sherry, and cook until most of the liquid is gone. Add the beef stock. Cook for about 30 minutes. Add salt to taste. and serve garnished with snipped chives and shredded cheese.
Slice the bread into eight slices, cutting on the bias to make the slices barely fit inside the bowls or crocks in which the soup will be served. Sprinkle about 2 Tbs. of shredded cheese over each slices. Place them on a baking pan and put them into the oven at 400 degrees. When the cheese melts and begins to bubble, remove the bread. Leave the oven on.
Ladle the soup into ovenproof bowls, cups, or crocks. Place a slice of bread, cheese side down, into each crock. Divide the remaining cheese among all the bread slices in the crocks. Put the crocks on a baking pan and put them into the oven until the cheese melts and browns a little. Serve immediately, warning guests that the soup is very hot.