Peel, wash and halve the potatoes and cook in boiling salted water for about 20 minutes. In the meantime, chop the nuts coarsely and roast them in a pan without fat, until golden brown. Put them on a flat plate and let them cool down. Clean and wash the beans and cook in boiling salted water for about 8 minutes. Drain, drain and quench. Wash mushrooms briefly in cold water, drain well, clean and rinse.
Dab the meat dry and spice strongly with salt. Heat 2 tablespoons of oil in a large frying pan and fry the meat on each side for 2-3 minutes. Remove, season with pepper, wrap in foil and let it rest in the preheated oven (electric cooker: 100 °C/ circulating air: 75 °C/ gas: see manufacturer).
Deglaze the frying pan with sherry and set aside. Drain the potatoes. Add milk and mash with olive oil to a coarse mash. Season to taste with salt, pepper and nutmeg. Keep warm. Heat 2 tbsp. oil with butter in a frying pan. Fry the mushrooms for about 3 minutes while turning.
Peel and finely dice the shallot. Heat 1 tablespoon of oil in a saucepan. Sauté the diced shallots until translucent. Add the beans with nuts and 2 tbsp. water and heat up for approx. 2 minutes, turning. Take meat out of the oven and wrap it in foil. Pour the resulting gravy into the frying pan. Heat up again briefly. Arrange the steaks on plates with broth, mashed potatoes, beans and mushrooms.