Cook the macaroni in salt water for about 8 minutes, then drain. In the meantime clean, wash and slice the mushrooms. Peel and finely chop the onion. Heat the fat. Sauté onion and mushrooms.
Season with salt, pepper and dried herbs. Dust flour over it and mix well. Add stock and cream while stirring constantly, bring to the boil and allow to cool. Beat the eggs and 5 tablespoons of cold water and stir into the mushroom sauce.
Clean and wash the zucchini and tomatoes and cut into very thin slices. Put half of the macaroni, if possible lengthwise, in a suitable form (high casserole dish; 1 litre capacity). Pour 1/4 of the mushroom sauce over it.
Then layer the zucchini slices, remaining macaroni and tomato slices. Pour the rest of the sauce over them. Sprinkle with parmesan. Cook in the preheated oven (electric cooker: 175 °C/ gas: level 2) for about 45 minutes.
In the meantime, boil 1/2 litre of water for the tomato sauce. Stir in the sauce powder with a whisk, cook for 1 minute. Sprinkle casserole with fresh herbs before serving. Serve in portions garnished with lettuce and tomato cubes.