Wash, peel and dice the potatoes. Clean, wash and drain the soup greens. Dice carrots and celery, cut leek into rings. Cut bacon into fine cubes.
Heat the oil in a pot and let the bacon in it crisp. Add potatoes and soup vegetables, sauté briefly and deglaze with stock. Add marjoram, bring to the boil, cover and cook for 15-20 minutes.
In the meantime wash parsley, dab dry and chop. Peel onions and cut into rings. Heat the fat in a pan and fry the onion rings until golden brown. Stir half of the parsley into the finished potato soup and season with salt and pepper.
Arrange in a terrine and serve sprinkled with roasted onion rings and remaining parsley.