This is an Indonesian recipe. The original recipe is for an oily fish, similar to our mackerel. However i'm not a great lover of oily fish so normally use a white fleshed fish - either haddock, pollock or cobbler. But any fish that fries well is suitable - mullet, bass, hake, trout and or salmon are suitable. This recipe is ideal for barbecues as the fish and the sauce don't come together until the final stage of assembly.
If you are using sambal olek instead of fresh chillies, be aware that this can be very salty, don't add salt until the final tasting.
Sambal olek is an Indonesian condiment and is just crushed red chilli preserved in salt, this is readily obtainable from any Chinese supermarket. Thai sweet basil is harder to get hold of but is available at some Chinese supermarkets. If you can't obtain Thai sweet basil use either normal basil or fennel (Thai sweet basil has a very strong aniseed taste).