Heat 4 tablespoons of the oil in a large heavy-bottom soup pan. Add garlic and cook for 2 minutes. Add the drained chickpeas, water, cumin and coriander. Bring to boiling, then reduce heat and simmer for 2 1/2 hours or until tender.
Meanwhile, heat remaining oil in a separate pan. Add the vegetables, cover and cook over medium heat, stirring frequently, for 20 minutes.
Stir the vegetable mixture into the chickpeas. Transfer half the soup to a food processor or blender and process until smooth. Return the purée to the pan, then add half the lemon juice. Taste and adjust lemon juice. Season with S&P. Heat through. Ladle into warm bowls and sprinkle with the chopped fresh cilantro and garnish with cilantro sprigs.