Sauté leeks and garlic in olive oil for 2 minutes.
Stir in barley, and cover with 2 cups of water; bring to the boil, then reduce the flame and cook on low for 10 minutes.
Add broccoli, cauliflower, Brussels sprouts, carrot, salt and 4 cups of water, stir. Bring the soup to the boil, lower the flame and cook for another 7 minutes or until vegetables are slightly softened. Season with black pepper and add thyme.