Trim the ends off the courgettes , cut in half lengthways and then into 1cm pieces.
Peel and finely chop the garlic and chop the mint.
Melt half the butter in a thick bottomed pan then add the courgettes and fry until soft. Add the garlic and season, then continue to cook, stirring to break up the courgettes.
Add the remaining butter and the mint. Smash about a third of the courgettes with a fork.
Meanwhile cook the penne in boiling salted water according to packet instructions until al dente. Drain, reserving a little of the cooking liquid. Add toi the sauce to loosen as preferred.
Stir in the penne and serve with the grated parmesan.