Finely chop the onion and garlic. Peel then dice the carrot and sweet potato.
Heat 1 Tbsp oil in a large pan, then gently soften the onion and garlic. Add the carrot and sweet potato bits, sauté for a 5 minute then add the lentils, paprika, cumin and oregano. Stir in the tomato purée, then add the stock and bay leaf. Bring to the boil and cook for 20 minute, until the lentils are tender.
Cut the bratwurst into rings and add to the soup (if it’s too thick, add more stock).
Cook for 8 minutes then add the shredded or sliced cabbage. Cook for 5 minutes.
Add the parsley, some ground pepper and a dash of vinegar just before serving.