Bring a large saucepan of water to the boil and add the sea salt. Meanwhile rinse the basmati rice under cold water. Rinse for around 1 minute and then put it in the saucepan of boiling water. Boil for 5 minutes.
In a large frying pan or wok over a medium heat add the oil, onion, garlic and chilli then fry for a minute then add the soy sauce; this is optional.
Add the prawns and chilli powder.
Whilst the prawns are heating remove the rice from the heat and drain in a colander . Add 2cm of water back in the saucepan and place the colander of rice over the saucepan. Cover the colander with foil and return to the heat for 8-10 minutes.
Add the sweet chilli sauce to the prawns and stir; reduce the heat and simmer.
When the rice is soft and fluffy remove some from the colander using a large spoon and add to a small domed bowl. Use the spoon to pat it down until the bowl is full. Take one serving plate and put it on top of the bowl then turn it upside down. This sandcastle style creates a small mound of rice. Of course this is optional but adds a nice touch to the dish.
Place the prawns around the rice and add one single prawn on top of the rice mound for a finishing touch.