Clean, wash and cut the leek into rings. Wash the meat and dab dry. Cut the bacon into small cubes and leave them crispy in a pan. Remove. Fry the meat in cooking fat for 1 minute on each side. Season with salt and pepper and take out.
Fry the leek in the same pan. Add 100 ml water and steam for 1 minute. Season with salt and pepper. Grease the casserole dish. Layer half of the leek. Add the schnitzel. Cover with the rest of the leek and bacon. Grate cheese. Mix half of the cheese with milk, cream and sauce thickener. Season with salt, pepper and nutmeg. Pour cream-milk mixture over the leek. Dice the toast and sprinkle the rest of the cheese over the casserole.
Cover with the rest of the leek and bacon. Grate cheese. Mix half of the cheese with milk, cream and sauce thickener. Season with salt, pepper and nutmeg. Pour cream-milk mixture over the leek. Dice the toast and sprinkle the rest of the cheese over the casserole. Cook in the preheated oven (electric cooker: 175 °C/ gas: level 2) for approx. 25 minutes. Garnish with parsley as desired