Lightly fry the leek in a frying pan with a dash of extra-virgin olive oil. Cut the asparagus into small pieces, add to the frying pan and lightly fry for a few more minutes. Next, break the broccoli into florets, remove the stems (put them by to make a tasty soup later), add to the frying pan and gently fry for a few more minutes. Add the thinly sliced carrots and keep cooking, stirring occasionally, until the vegetables are cooked al dente.
Boil the spaghetti in salted water, strain and when the vegetables are ready, add to the frying pan. Warm everything through for a few minutes.
Sprinkle some grated Parmesan cheese on top before serving.