Heat olive oil in a large pot or Dutch oven over medium heat. Add onion, carrots, and celery and sauté for 3-4 minutes until softened. Add garlic, salt, and pepper and cook for another minute until fragrant.

Add mushrooms and sauté for 4-5 minutes until the liquid releases and the volume is reduced. Scrape up any browned bits from the bottom of the pot.

Stir in barley, tomato paste, soy sauce, thyme, and bay leaf. Add vegetable broth and bring to a boil.

Reduce heat to a simmer, cover, and cook for 40-45 minutes, or until barley is tender.

Remove bay leaf. Season with salt and pepper to taste. Garnish with parsley and chives before serving.