Bring barley and 3 cups water to a boil over high heat. Reduce heat and simmer 30 minutes. Drain and set aside when barley is tender and cooked through.
In a large soup pot over medium heat, add the oil, onion, and celery. Cook, stirring occasionally, until onions are translucent and edges begin to brown, about 10 minutes.
Add any uncooked vegetables--in this case I had a small amount of raw potato, celery root, and cauliflower--along with the garlic, dry herbs, salt and pepper. Continue to cook until vegetables soften (add oil as needed), about 10 minutes.
Add the broth, bay leaf, and Parmesan rind to the vegetables and bring to a low boil. Stir-in gravy, tomatoes, peas, (leftover) cooked vegetables, barley, and meat. Bring to a simmer and cook for 30 minutes to meld flavors.
Stir-in parsley the last 5 minutes of cooking, adjust seasoning for salt and pepper, to taste. Serve hot.
**This is optional, but does bring a deeper flavor to the soup. Allowing extra beef stock to simmer on the stove for an hour to reduce and concentrate is a good substitute.If using a pressure cooker, cook for only 8-10 minutes in STEP 3.