Heat a large wide pan and dry-fry the curry paste with the onions for 4-5 mins until the onion begins to soften. Add the rice to the pan and stir to coat in the curry paste. Add the stock, then bring to the boil.
Cover the pan and turn the heat down to low. Leave the rice to simmer slowly for 12-15 mins until all the liquid has been absorbed and the rice is cooked. Turn off the heat and stir in the prawns, peas and chilli. Cover the pan and leave to stand for 5 mins.
Fluff up the rice grains with a fork and season if you want. Scatter over the coriander and serve with lemon wedges.