Wash the potatoes and cook in boiling water for about 20 minutes. Drain, rinse with cold water and peel. Defrost spinach in a sieve. Clean and wash the peppers and cut them into thin rings.
Wash the meat, dab dry. Heat oil in a pan. Brown the meat on both sides. Remove and season with salt and pepper. Melt the fat in a saucepan. Sauté flour in it.
Add milk while stirring, bring to the boil and season with salt, pepper and nutmeg. Cut potatoes into thin slices. Grease a large casserole dish. Add some sauce. Then alternately layer potatoes, peppers, spinach, sauce and meat.
Add another layer of spinach, peppers, sauce, potatoes and gravy. Bake in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 2) for about 40 minutes. Sprinkle Parmesan cheese over the casserole 10 minutes before the end of the baking time.
Garnish with parsley.