Preheat the oven on to 180°C.
Peel the sweet potatoes and cut them into 3 cm chunks.
Put the tomatoes, still on the vine, in a large roasting dish.
Cut the onion in half. Tuck these between the tomatoes together with the sweet potatoes and garlic cloves.
Scatter the thyme leaves, then drizzle the oil over the vegetables. Season with sea salt and freshly ground black pepper.
Roast for 15-20 minutes, or until they soften and the tomatoes have started to burst.
Transfer the roasted vegetables and jus into a pan. Discard any burnt onion & tomato skin together with the garlic skin and tomato vine. Add the garlic flesh to the pan.
Add the stock pot and about 500 ml water. Bring to the boil. Add half of the drained chickpeas, and cook for another couple of minutes. Turn off the heat, and (using a stick blender) process the stew until you get a textured or smooth soup (whichever you prefer). Add more water or stock if the soup is too thick.
Add the chopped herbs and the remaining chickpeas and warm it up.
Serve warm.