Wash the schnitzel and dab dry. Heat 2 tablespoons of oil in a large frying pan. Fry the cutlets in it while turning them in 1-2 portions. Season meat with salt and pepper and place them flat next to each other in an ovenproof dish.
Clean, wash and cut the leek into rings. Clean the mushrooms and, depending on their size, halve or slice them. Dice bacon.
Heat 2 tablespoons of oil in a large frying pan, drain the bacon in it until crispy and take it out. Sauté the mushrooms in the hot bacon fat while turning, season with salt and pepper. Sprinkle flour over the mushrooms and sauté briefly. Add stock and cream and bring to the boil while stirring. Add leek, bacon and dried marjoram and simmer covered for about 5 minutes. Stir in between. Season mushroom-porree-cream with salt and pepper and pour over the escalopes.
Cover and braise in a preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: level 2) for approx. 1 3/4 hours. After about 1 hour remove the lid and braise. Garnish with fresh marjoram.