Bring a large saucepan of salted water to the boil.
Meanwhile, pat the prawns dry with kitchen paper, then mince the garlic and chop the parsley.
Cook the squid-ink pasta in the boiling water according to the packet instructions until al dente. Drain, reserving about 250ml of the cooking water.
Heat the olive oil in a large frying pan over medium-high heat. Add the garlic and chilli flakes and fry for 30 seconds until fragrant.
Add the prawns in a single layer and cook for 1-2 minutes on each side until pink and opaque. Transfer to a plate and set aside.
Pour in the white wine or chicken stock, scraping the pan to loosen any browned bits. Simmer for 1-2 minutes until slightly reduced.
Reduce the heat to medium-low, stir in the butter until melted, then add the parsley.
Add the drained pasta to the pan and toss well, adding a little of the reserved cooking water as needed to coat.
Return the prawns to the pan, gently toss to combine, then season with salt and pepper.
Serve immediately with a squeeze of lemon.