Watercress soup (is truly anti-oxidant, especially protective againts lung cancer, rich in iron)

Directions

Heat the oil in a large saucepan and saute the onion gently until soft, Add garlic and continue to cook for 2 minutes. Add the watercress and continue to cook gently until it wilts. Add the stock and simmer for about 10 minutes than transfer to a blender or food processor and whiz until smooth.

Serve hot or cold with a swirl of yogurt in each bowl.