Heat the oil in a large saucepan on medium heat and sauté the ground ingredients until fragrant, for 2-3 minutes.
Add prawns and coat thoroughly, then add the pineapples and do the same.
Add the coconut milk and bring to a gentle boil on low heat (coconut milk will curdle over high heat).
Add the tamarind, lime juice, salt and sugar and cook for 5 minutes until prawns are done.
If you'd like more gravy, add some water (about 125ml/half a cup) or the equivalent amount of coconut milk for a slightly creamier curry.
Add the leaves that you're using a minute or so before the end of cooking time, turn off heat and serve with plain boiled rice. If using coriander leaves, chop and scatter after turning the heat off.