Peel, rinse and coarsely chop carrots and potatoes. Cook in a little clear soup with the lid closed. In the meantime, chop the onions and cut them into wedges. Heat oil in a cast-iron frying pan, fry mince briefly in it. Add onions, steam for about 15 minutes, drain vegetables, mash coarsely with a potato masher. Stir in crème fraîche. Season with salt, pepper and nutmeg. Rinse marjoram, shake dry – except for a few leaves – chop coarsely and fold in.
Carrot-potato puree on the fat form and sprinkle with cheese. Bake in the heated oven (at 200 degrees /circulating air) for about 15 minutes until golden brown. Garnish with the remaining marjoram leaves.