Sort and wash the spinach. Peel onion and garlic, dice finely and fry in 2 tablespoons of hot oil. Add the spinach dripping wet and let it collapse. Season with salt, pepper and nutmeg.
Rinse cutlets cold and dab dry. Fry in the remaining oil on each side for about 5 minutes. Season with salt and pepper. Drain mozzarella and cut into slices. Cover each cutlet with some spinach and mozzarella.
Bake briefly in a preheated oven (electric oven: 200 °C/ gas: level 3).