Peel and finely dice the onions. Clean, clean and slice the mushrooms. Melt 50 g butter in a pot, fry onion in it until transparent. Add the mushrooms and stew for 8-9 minutes. Season with salt and pepper. Add cream and bring to the boil
Meanwhile wash the meat, dab dry and cut into strips. Heat the oil in a large frying pan and fry the meat in it, turning it over if necessary in portions. Season with salt and pepper. Deglaze with stock, bring to the boil
Cook the pasta in boiling salted water according to the instructions on the packet. Drain, quench and drain well. Add pasta, meat with broth and sour cream to the mushroom mixture, mix well. Season again with salt and pepper. Wash parsley, shake dry and cut to 1 leaf for garnishing. Stir parsley into the mushroom mixture, except for 1/2 tbsp for garnishing.
Place in an ovenproof dish and sprinkle with cheese. Spread 40 g butter in flakes on top. Bake in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for 15-18 minutes. Remove from the oven, sprinkle with parsley and garnish