1) In a saucepan, melt the butter and cook the onions gently till tender.
2) Add the stock and bring to a boil, stirring with a fork.
3) Add the rice, cover and simmer gently for about 25 minutes, till the rice is soft and the water has been absorbed.
4) Season the prawns with salt and pepper and sprinkle with the lemon juice.
5) Add the prawns to the rice and heat for 2-3 minutes, till the prawns are piping hot.
6) Pile the prawn pilaf into a warmed serving dish and sprinkle the chopped prasley all over. Serve right away.