Halve the courgettes lengthways, then finely slice at an angle. Peel and finely slice the garlic, then deseed and finely slice the chillies. Pick and roughly chop the herbs.
Cook the pasta according to the packet instructions.
Melt the butter with a splash of oil in a large frying pan on a medium heat. Add the courgettes and cook until slightly browned.
Add the garlic, chilli and prawns, then cook until the prawns are cooked through. Take off the heat and squeeze over the lemon juice.
Drain the pasta once cooked, reserving a little cooking liquid. Add the pasta to the frying pan and toss with the courgettes and prawns. Add some cooking liquid if it looks a little dry, then stir in the dill or parsley.
Season to taste and serve at once, with a grating of Parmesan, if you like.