After washing the zucchini, chop off both tips and cut lengthwise into thin strips. Arrange zucchini strips on a tray or baking sheet. Do this in batches. Sprinkle with salt and let them rest for 10 minutes to release the moisture. Then blot with a towel.
Melt the butter in a frying pan set over medium heat.
Sauté the mushrooms with the onion and garlic in the pan for a minute. Salt and pepper just to taste.
Mix in the tomato and beef and allow to cook for another 3-5 minutes. Simmer for 5 more minutes, enough to thicken the sauce to your liking. Set aside.
Crack the egg in a medium bowl. Add the Parmesan cheese and heavy cream, and beat together.
Prepare a baking dish for the lasagna. Layer a bed of meat on the base of the dish, arrange the zucchini slices on top of the meat, and finally pour the egg and cheese mix on the surface. Continue with the remaining lasagna layers until the rest of the ingredients are all used up.
Sprinkle the mozzarella cheese on top.
Set the oven to 340°F and bake the dish inside. Leave for about 20-30 minutes until the cheese turns golden and melted.
Allow to cool for another 3 minutes then serve.
Serve sprinkled with chopped basil and your favorite veggies (optional).