This is an excellent vegetarian soup for lentil lovers. It's so warming for winter meals and can be taken to work in a thermos mug ready to enjoy for lunch. If you don't have brown lentils, use red ones or the French green puy lentils. If you prefer sweet potato, you can swap that for the desiree potatoes. Add extra herbs too if you like and consider topping it with a dollop of basil pesto. Enjoy!