Leftover Prime Rib and Barley Soup

Ingredients

• 1 tablespoon avocado or olive oil
• 1 cup chopped carrots, from 2 medium carrots
• 1 cup chopped celery, from 2 stalks of celery
• 1 shallot, finely chopped (1/4 cup)
• 1 cup (2 ounces) sliced shiitake or cremini mushrooms
• 1 teaspoon fresh thyme leaves
• 1 tablespoon soy sauce or Tamari
• 12 ounces (1 ½ lbs.) cooked Prime Rib, cut into ½-inch pieces
• 6 cups beef broth
• Kosher salt, as needed
• Freshly ground black pepper, as needed
• 2 cups cooked pearled barley (1/2 cup uncooked), prepared according to package instructions