Heat two thirds of the olive oil and add the finely chopped garlic. When it begins to turn coulour add the tomatoes with their juice, squashing them with a wooden spoon. Add salt and pepper to taste. Cook briskly for 15 minutes.
Meanwhile, heat the rest of the oil in a separate pan and add the mushrooms which have been wiped with a damp cloth and then finely sliced. Lightly salt the mushrooms and let them cook gently for 5 minutes. Add the chopped parsley and keep warm.
Cook the pasta, following packet directions carefully to avoid over-cooking. Drain the pasta and turn into a heated serving dish. Add the tomato sauce, stirring thouroughly, and then the mushrooms. Stir well and serve at once.