Clean and wash the zucchini and mushrooms. Quarter the zucchini lengthways and cut into slices. Halve or quarter the mushrooms, peel the onion and cut into fine cubes. Sauté together in hot fat. Add milk and cream. Season with salt and curry. Cover and cook for about 10 minutes.
In the meantime, cook the spaghetti in salted water until al dente. Thicken the zucchini sauce with a sauce thickener and season with salt and lemon juice. Stir in the chopped parsley. Pour the sauce over the spaghetti and serve sprinkled with grated cheese.