Fire up The Bastard to 180 °C. Put the cast-iron pan on the grill and let it get hot. Chop the onions and finely chop the garlic. Cut the red chillies into rings. Heat the oil in the cast-iron pan and fry the onions, garlic and chillies, along with the laos and turmeric, until everything is light brown.
Chop the salam, lime leaf, lemon grass and the kemiri nuts very finely. Add this to the mixture in the cast-iron pan together with the lemon slices and the kentjur. Fry for a further 5 minutes, then add the coconut, sugar and water. Boil everything down to a nice paste, season with some salt if necessary. The boembu is ready.
Remove the lemon segments, the laos and turmeric from the cooled down bean curd. Lay the fillets of mackerel on the skin side on a piece of aluminium foil. Cover one of the mackerel fillets with an inch of bean curd. Lay the other fillet on top and roll it up tightly in the aluminium foil. Put the fish for 20 minutes at 180 degrees on The Bastard.
Delicious with sweet and sour cucumbers or atjar, sugar snaps and boiled rice.