Peel and chop the onion. Clean, clean and slice the mushrooms. Wash the meat and dab dry. Wrap 2 slices of bacon around one fillet each. Heat 2 tablespoons of oil in a frying pan, fry the meat well all around, season with salt and pepper and remove.
Add 1 tablespoon of oil to the pan and heat. Sauté the mushrooms in it while turning. Add the onion and fry briefly. Season with salt, pepper and paprika. Deglaze with stock and cream, bring to the boil and stir in the sauce thickener.
Bring to the boil again, season with salt, pepper, paprika and sugar. Put mushroom cream and meat into an ovenproof dish, sprinkle cheese over it and bake in a preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for 20-25 minutes.
Wash the parsley, shake dry, put a leaf aside for garnishing. Cut the remaining parsley into fine strips. Remove the casserole from the oven, sprinkle with parsley and garnish.