Instructions

1. Roughly chop the fennel and onion. Set aside the fronds of the fennel.
2. Heat in a heavy-based saucepan over medium heat. Add the onion and fennel and gently sauté for 5 minutes, stirring regularly.
3. Meanwhile, peel the kohlrabi and potato, then cut them into small cubes.
4. Add them to the onion, then add the caraway seeds and bay leaf and stir for a minute.
5. Pour in the stock and simmer for about 20 minutes, until the veggies are tender.
6. Discard the bay leaf.
7. Using a hand-held blender or liquidiser, process the mixture until you get a smooth, velvety soup. Add more stock if you think it's too thick.
8. Add the drained beans, then warm up the soup.
9. Add the apple cider vinegar. Taste, then season with salt and pepper, if needed.
10. Chop the fronds and scatter on top of the soup, when served.