Clean, wash and thinly slice the zucchini. Clean the mushrooms and cut them into thick slices. Wash, peel and slice the potatoes very thinly. Grease a gratin dish. Put zucchini, potatoes and mushrooms in a fan shape in the dish.
Mix cream and eggs and season with salt, pepper and nutmeg. Pour over the gratin and sprinkle with parmesan. Bake in the preheated oven (electric: 200°C/ gas: level 3) for about 45 minutes. In the meantime peel garlic and onion. Finely dice the onion, press the garlic through a garlic press. Cut avocados in half, remove stone and peel the fruit halves. Pour lemon juice over the fruit flesh and puree. Stir in garlic and onions. Season to taste with salt and cayenne pepper and place in a bowl.
Cut avocados in half, remove stone and peel the fruit halves. Pour lemon juice over the fruit flesh and puree. Stir in garlic and onions. Season to taste with salt and cayenne pepper and place in a bowl. Roast the pine nuts in a pan without fat, let them cool down and sprinkle over the avocado cream. Serve together with the zucchini gratin