Finely the onion and garlic. Peel the sweet potato and cut it into chunks. Slice, then roughly chop the red the cabbage.
In a large pot, heat the oil, then sauté the onion for 5 minutes. Add the garlic and the spice seeds and stir for a minute, then add the chopped vegetables. Add the other spices and stir to coat the veggies.
Pour in the stock and bring to the boil.
Cover with a lid, turn down the heat and gently simmer for 25 minutes.
Drain the beans and add them to the soup. Cook for 5 minutes, then turn off the heat and add the fresh herbs.
Using a stick blender, blitz until you get a textured soup. Add the vinegar and plenty of black pepper. Add more stock if you find the soup too thick.
Reheat if necessary, then serve.