Top and tail the courgettes, then cut them into long, thin strips.
Prepare the gremolata by very finely mincing the garlic with the parsley, then mix in the lemon zest.
Bring a large pan of water to a boil for the pasta.
Working in a large frying pan, fry the onion and a pinch of salt in the olive oil until the onion starts to soften.
Add the courgettes and fry until both are soft and floppy.
Meanwhile, salt the boiling water, drop in the spaghetti, then set a timer.
Keep a close eye on the timings; a minute before the pasta is ready to come out, add the prawns and gremolada to the courgettes (if the prawns are cooked, they will need just seconds; if they are raw, they will need a minute or so).
Lift the spaghetti directly into the courgette pan with a little of its cooking water clinging to the strands, then toss thoroughly.
Serve with little more olive oil on top.
