Dice the rolls and the bacon. Fry the bacon in a frying pan, add the onions and fry until translucent (add a little more clarified butter if needed). Put the mixture in a small baking dish form. Heat the milk.
Heat the clarified butter in a frying pan and toast the bread cubes in it until golden. Put them into a large enough bowl, pour the hot milk over them and let them swell for at least 10 minutes. Add bacon, onion, marjoram, parsley, egg yolk to the rolls, season with salt, pepper and nutmeg and mix well. Whip the egg whites until stiff and fold into the dumpling mixture.
Fill everything into a buttered gratin dish. Place in a water bath and cook in the oven at 180 °C for about 20 minutes.