Peel and pinch the vegetables and cut the bacon into small cubes. Sweat a little, dust with the flour and cook with the broth. Puree the potatoes and add to the soup. Bring to the boil until the whole thing is creamy. Season to taste with salt, pepper and marjoram.
Cut the black pudding into slices and fry.
Divide the soup on the plates. Serve garnished with chopped parsley and black pudding slices.