Dice the bacon. Clean, wash and halve the mushrooms. Clean, wash and cut leek into rings. Peel and finely dice onion.
Fry the bacon in a large pan without fat until crispy. Remove. Dab meat dry and fry in bacon fat for 2-3 minutes on each side. Season with salt and pepper and take out. Heat oil in hot frying fat.
Sauté the mushrooms in it, season with salt and pepper. Fry onion and leek briefly. Add bacon again.
Deglaze with cream, bring to the boil. Season to taste with salt and pepper. Put cutlets in an ovenproof dish. Spread mushroom vegetables over it. Close the mould well with aluminium foil. Bake in a preheated oven (electric cooker: 175°C/circulating air: 150°C/gas: level 2) for approx. 1 3⁄4 hours.
Finely grate the cheese. Peel and wash the potatoes, cover and cook in salted water for about 20 minutes. Remove aluminium foil from the mould. Spread the cheese on the cutlets and bake at the same temperature for 20-25 minutes.
Wash parsley, shake dry and chop finely. Sprinkle hazelnut leaves on the escalopes about 5 minutes before the end of the baking time. Drain the potatoes. Add milk and butter and mash everything.
Season the puree with salt and nutmeg. Sprinkle schnitzel with parsley. Add mashed potatoes.