This soup is great for winter lunches, served with coriander and an English spinach side salad.
Fry the onion and garlic in the olive oil for a few minutes.
Add the sweet potatoes, tomatoes, tomato puree and water, broth or stock and simmer until the potatoes are just tender.
Add the salt and fresh ground black pepper.
Allow to cool slightly then puree until smooth and creamy with no lumps.
Serve with cultured sour cream and fresh herbs sprinkled on top.