1. Chop onion, carrots and sweet potato.
2. Heat the oil in a large saucepan.
3. Add the onion and cook over a medium heat for 5 mins or until golden.
4. Add in the carrots, lentils, sweet potato, and tomato puree. Mix well
5. Add the stock and bring to the boil.
6. Boil uncovered for 5 mins, then reduce the heat, cover and simmer for 20 minutes or until the sweet potato, carrots and lentils are tender.
7. Stir through the parsley.
8. Blitz the soup with a handheld blender until smooth.
9. Serve with a dollop of yogurt.
Suitable for freezing.