Trim fresh mushroom stems and slice thickly; slice shallot thickly. Put vegetables in a roasting pan and toss with olive oil, salt and pepper. Lay beef ribs on top of vegetables and salt and pepper. Put in preheated oven and immediately turn heat down to 350 degrees.
Soak dried mushrooms in 4 cups boiling water until soft, about 20 minutes. Lift from water with slotted spoon and dry on paper towels, squeezing to remove water, and chop roughly. Use mushroom water to make bouillon (or, if using fully constituted broth, dump mushroom water).
When beef reaches 200 degrees on a meat thermometer -- about 1 hour at 350 -- pull from bones and tear into bite-sized pieces with a fork. Put beef, rehydrated mushrooms, roasted vegetables and broth into a soup pot. Bring slowly to a low-boil. Add quick cooking barley and simmer 15 minutes or until barley is chewy-soft.
(If you can't find quick cooking barley, put just the broth and regular barley soup pot, bring to a boil and simmer for about 45 minutes, then add beef and vegetables for last 15 minutes of simmering.)
Serve with fresh chopped parsley, and salt and pepper to taste.