Heat the oil in a medium-large pot over medium-high heat for about 2 minutes.

Add chopped onion, minced garlic, and thinly sliced carrots. Sauté for approximately 4 minutes, until onions are soft.

Toss in sliced brown mushrooms and sauté for another 3 minutes until they begin to brown.

Add barley and enough water to cover by 4 inches, around 5-6 cups. Add vegetable stock powder, salt, and pepper.

Bring the mixture to a boil, then reduce heat to low and cover. Simmer for about 1 hour.

For slow cooker, transfer sautéed vegetables, water, barley, and seasonings. Cook on low for 6-7 hours.

Ladle the soup into bowls and garnish with finely chopped parsley.