Drain the chickpeas, rinse under cold running water and drain again. Put the bacon joint in a large, deep saucepan and cover with cold water. Bring the water briefly to the boil, then drain, discarding the water.
Transfer the bacon joint to a clean, large heavy-based saucepan. Add the chickpeas, studded onion, garlic, bay leaf, thyme, marjoram, parsley and measurement water. Bring to the boil, then reduce the heat, partially cover and simmer for 1½ hours until the meat is tender.
Remove and discard the onion and herbs. Remove the hock, transfer to a board and cut into small pieces. Set aside. Add the stock, potatoes and cabbage to the pan, and simmer for a further 30 minutes.
Add the reserved hock pieces to the soup and cook for a further 10 minutes. Season with salt and pepper. Ladle the soup into warm soup bowls and serve with fresh, crusty bread.