For the sauce, soak porcini mushrooms in 400 ml of cold water for about 1 hour. Wash and quarter the pumpkin and scrape out the seeds with a spoon. Cut the pumpkin and its skin into large pieces. Grate parmesan finely.
Preheat the oven (electric cooker: 200 °C/circulating air: 175 °C/gas: see manufacturer). Wash potatoes thoroughly, cut in half lengthwise. Cut surface several times lengthwise and crosswise, but do not cut through.
Put the potatoes on a baking tray. Season with salt, sprinkle with parmesan and spread butter in pieces on top. Mix pumpkin with 2-3 tablespoons of oil, season with salt and pepper. Add to the potatoes on a baking tray.
Bake in a hot oven for about 40 minutes.
Clean the mushrooms, possibly wash and slice them. Peel and finely chop the onion. Pour the porcini mushrooms into a sieve lined with kitchen paper, collecting the soaking water. Chop the porcini finely.
Pat the steaks dry. Heat 2 tablespoons of oil in a large frying pan. Fry the steaks in it at high heat for 1 minute on each side, then continue to fry at medium heat for 2-3 minutes on each side. Season with salt and pepper.
Remove and keep warm wrapped in foil.
Sauté the mushrooms in hot frying fat. Briefly fry the onion and porcini mushrooms. Dust with flour and sweat. Stir in sherry, soaking water and sour cream, bring to the boil and simmer for about 5 minutes. Season to taste with salt and pepper.
Wash the chives, shake dry and cut into fine rolls. Arrange steaks with sauce, potatoes and pumpkin. Sprinkle with chives.