In a pan, fry the mince with the onion until browned. Add the mushrooms and fry for 1-2 minutes.
Stir in the contents of the sachet along with the tomatoes. Bring to the boil, stirring constantly.
Reduce heat, cover and simmer for 15 minutes, stirring occasionally.
Serve with the spaghetti and a sprinkle of Parmesan cheese.