Preheat the oven for the fan-shaped potatoes (electric oven: 175°C/circulating air: 150°C/gas: see manufacturer). Grate the parmesan. Peel, wash and cut the potatoes close together, but do not cut through.
Place in a casserole dish. Sprinkle with 2 tablespoons of oil and season with salt and pepper. Bake in a hot oven for 40-45 minutes. Melt 2 tablespoons of butter. After about 30 minutes, brush the potatoes with the liquid butter.
Sprinkle with breadcrumbs and parmesan and finish baking.
In the meantime peel and chop the onion. Clean and wash the mushrooms and if necessary wash them briefly. Cut large mushrooms smaller. Wash and clean the beans and cut them into pieces. Cover and cook in boiling salted water for about 10 minutes.
For the medallions dab the meat dry. Wrap 1 slice of bacon around each medallion and tie with kitchen string. Heat 1 tablespoon of oil in a frying pan. First fry the bacon on all sides, then fry the steaks on each side for 3-4 minutes.
Season with salt and pepper. Wrap in aluminium foil and let it rest for about 8 minutes.
Heat 1 tablespoon of oil in the frying fat. Fry the mushrooms for 2-3 minutes while turning. Add 2 tablespoons of butter and fry for another 2 minutes. Season with salt and pepper. Sprinkle 1 tablespoon of sugar over it, caramelise briefly.
Deglaze with vinegar and 5 tablespoons of water, bring to the boil and simmer for 1-2 minutes. Season to taste with salt, pepper and sugar.
Drain the beans in between. Heat 1 tablespoon of butter in the pot. Brown the onion in it. Add the beans again and toss them in. Wrap medallions out of the foil and pour the resulting roast to the mushrooms.