Tender bits of prime rib, hearty barley, paired complimentary vegetables for one delicious bowl of soup. Place the butter into a large Dutch oven over medium heat, and let melt. Add in the celery, carrots, and onion. Let cook for 5-6 minutes, until softened and starting to brown. Add in the garlic and stir for 30 seconds.
Bring barley to a low boil. In a sauce pan bring the second portion of beef broth (3 cups) to a boil. Add the barley and cook at a low boil over medium heat until al denté, or about 20 minutes. Transfer the barley. The liquid will not be absorbed completely, do not drain off excess broth. Add the broth and cooked barley to your soup.
2 cups chopped leftover prime rib (including what comes of the bones after cooking the broth) Heat the olive oil in a large Dutch oven (6-8 quarts) or soup pot over medium high heat. Add the bones from the prime rib and sear for 2-3 minutes on each side, allowing some of the fat to render from the bones.
Prime rib and broth. Add the cut portions of your leftover prime rib (or roast beef, pot roast, or leftover steak) along with the first 6 cup portion of beef broth. Stir, cover, reduce the heat to low, and simmer for about 70-75 minutes. Wait to start the barley. Start cooking your barley (below) after about 45 minutes of simmering the soup.