Sort the spinach, wash thoroughly and drain. Put the spinach in little boiling salted water, let it collapse for a short time and let it drain on a sieve. Peel onion and garlic.
Finely dice onion, press garlic through a garlic press. Wash and quarter the tomato and remove the seeds. Cut the tomato quarters into small cubes. Clean the mushrooms, break out the stems and dice finely.
Heat the fat in a frying pan. Lightly fry the onions, mushroom stems and garlic in it. Stir in spinach, tomato and cream cheese and season with salt, pepper, marjoram and nutmeg. Sprinkle the inside of the mushroom caps with salt and pepper and spread the spinach filling inside the caps.
Place in an ovenproof dish. Pour cream and broth and sprinkle the mushrooms with parmesan. Bake in a preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for approx. 40 minutes.
Arrange on a plate and garnish with lemon wedges and fresh marjoram. Fresh baguette tastes good with it.