To make the sauce carefully open the can of coconut milk and remove 4 tbsps of the thick cream. Stir the remaining contents of the can well and set aside.
Pour 2 tbsps oil into a large non stick frying pan and set over a medium heat. When the oil is hot add the coconut cream and the green curry paste. Stir and fry until the oil separates and the paste is lightly browned.
Reduce the heat to low and add the fish sauce, tamarind, sugar, reserved coconut milk and 2 tbsps water. Stir and bring to a gentle simmer. Check the flavours adding more fish sauce, tamarind or sugar as needed.
Just before serving pour the remaining oil into a separate large non stick pan and set on a medium high heat. When the oil is very hot add half the scallops in a single layer and let them brown slightly on one side. Turn over and brown the other side. Remove to a bowl and brown the remaining scallops the same way.
Heat the sauce and add the scallops. Stir gently for 2-3 minutes or until just cooked through.
Tear the lime leads or remove the central vein and shred, Scatter over the scallops together with the basil leaves to serve.