1. Cook the barley in boiling water until tender. Drain. 2. In a heavy saucepot or stockpot, sweat vegetables in the fat until about half-cooked. Do not let them brown. 3. Add the chicken stock. Bring to a boil. Reduce heat and simmer until vegetables are just tender. 4. While the soup is simmering, sauté the mushrooms briefly in fat without letting them brown. 5. Add mushrooms and drained, cooked barley to the soup. Simmer another 5 minutes. 6. Degrease the soup. Season to taste with salt and pepper.