Wash and dice the sweet potatoes into small pieces. Place in a large saucepan with the crushed garlic and fill with enough water to cover the potatoes completely. Boil for 20 minutes or until the sweet potatoes are soft.
Allow to cool slightly, then place the potatoes and garlic in a food processor, along with the liquid broth it was cooked in and half a tin of fava beans. Blend on a low-medium setting for 1-2 minutes or until you are satisfied with the consistency.
Pour the soup back into the large saucepan and return to the heat. Season with a pinch of crushed chilli flakes, dried thyme, mild curry powder and salt to taste. Add the other half of the tin of fava beans and a little water (as needed). Heat the soup for about 5 minutes.
Serve hot and garnish with a handful of chopped fresh parsley.