Peel and finely dice the onions. Cut meat into strips. Clean and trim the mushrooms and halve them according to size. Wash rosemary, shake dry, pluck needles from the stems and cut finely.
Peel, wash and roughly grate the potatoes. Mix potatoes, egg, potato flour and about half of the onions well. Season with salt, pepper and nutmeg.
Heat 2 tablespoons of oil in a frying pan. Sauté the meat in it, turning it over, season with salt and pepper and remove from the pan. Add 2 tablespoons of oil to the pan and heat. Sauté the mushrooms well.
Add the rest of the onions and rosemary, except for a little to garnish, and fry briefly. Season with salt and pepper. Sprinkle with sugar, allow to caramelize slightly, deglaze with vinegar and 125 ml water.
Bring to the boil and simmer for 4-5 minutes.
In the meantime heat up the clarified butter in portions in a large pan. Pour the potato mixture into the pan in portions the size of a spoon, press flat with the back of the spoon and fry until golden brown, turning.
Remove from the pan and keep warm. Add the meat to the mushrooms, heat briefly, season again with salt and pepper. Arrange the shredded meat in a pan, sprinkle with rosemary and garnish.