Clean, wash and break the beans into pieces. Cook in 1/2 litre of boiling salted water for about 7 minutes. Pour off, catch the vegetable water. Add stock. Peel, wash and roughly dice potatoes and celery. Peel and chop the onion, fry in hot oil with the potatoes and celery.
Pour on the stock and cook covered for about 20 minutes. Puree with a chopping stick, stir in cream. Add the beans. Wash the marjoram, pluck the leaves from the stalks. Season soup with salt, pepper and marjoram. Cut ham into cubes and sprinkle over the soup