Roasted Carrot Soup

INGREDIENTS

• Salt
• 6 to 8 large carrots (about 1 3/4 pounds)
• 1/2 large sweet onion, chopped
• 1 piece ginger, an inch long, peeled
• 2 large garlic cloves, chopped
• Freshly ground black pepper
• 1 sprig thyme, plus more for garnish
• 6 cups vegetable stock (good quality, not too high in sodium)
• 1/4 cup olive oil