Clean, trim and quarter the mushrooms. Wash and drain the spinach. Whisk eggs and cream in a bowl. Season to taste with salt, pepper and nutmeg
Heat the oil in a pan (22 cm Ø). Fry the mushrooms for about 4 minutes. Add spinach. Pour egg-cream over it and let it simmer at low heat for 7-8 minutes
Cut the mozzarella into pieces. Spread the mozzarella on the omelette about 2 minutes before the end of the cooking time and let it melt