Heat 1 tablespoon of olive oil in a large Dutch oven over medium-high heat. Add the beef in batches and cook for 2-3 minutes, or until caramelized.
Once the beef is cooked, add the onion and garlic and cook for an additional 2-3 minutes, stirring often.
Add the beef broth and bay leaves, and season with sea salt and freshly cracked pepper, to taste. Cover the Dutch oven with a lid and place it into the oven for 2-3 hours.
Heat the remaining tablespoon of olive oil in a large skillet over medium-high heat. Add the mushrooms and cook for 3-4 minutes, until golden brown.
Add the mushrooms, carrots, celery, fingerling potatoes, and pearled barley to the beef soup.
Cover and cook on the stovetop over medium-low heat for 45-60 minutes or until the vegetables are soft and the pearled barley is cooked through.
Mix the cornstarch with water and stir until completely dissolved. Add the cornstarch slurry to the boiling soup and stir.