Warm up the milk. Crumble yeast into it and dissolve it. Put flour, 1 egg, fat, sugar, salt and yeast milk into a bowl and work through with the dough hooks of the hand mixer until the dough starts to bubble.
Cover and leave in a warm place for about 30 minutes. In the meantime peel onions and cut them into rings. Cut bacon into strips. Heat oil in a pan and fry onion rings in it in portions, take them out.
Brown the bacon pieces in the pan and let them drain on kitchen paper. Grate cheese finely. Wash the marjoram, dab dry and chop finely. Mix crème fraiche and 4 eggs until smooth. Season with salt, pepper and nutmeg.
Stir in the marjoram. Grease a baking tray (32 x 38 cm) and sprinkle with breadcrumbs. Knead the yeast dough briefly and roll out thinly in the fat pan. Press the dough up at the edge with your hands.
Prick the dough several times with a fork. Spread onion rings on top, spoon egg-crème fraîche on top and sprinkle with cheese and bacon. Bake in the preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: level 2) for about 45 minutes.
Take out and let it cool down a little. Cut into pieces and garnish with marjoram.