First make the nasi goreng paste; put the paste ingredients into a food processor and blend until smooth.
Cook the rice in boiling salted water for 15 minutes, until just tender. Drain, rinse well and then spread it out on a tray and leave until cold.
Preheat the grill to high. Season the mackerel on both sides with salt and pepper.
Lay them on a lightly oiled baking tray or the rack of a grill pan and grill for 4 minutes on each side. Leave them to cool and then flake the flesh into large pieces, discarding the bones.
Next, beat the eggs with salt and pepper then heat a little oil in a frying pan and make three omelettes. The object is to get them as thin as possible. Cook each one till the egg has lightly set on top, then flip over and cook a few seconds on the other side.
Roll the omelettes up, leave to cool then thinly slice.
Pour 1cm/½in of sunflower oil into a frying pan. Add the shallots and fry over a medium heat until crisp and golden brown. Lift them out with a slotted spoon and leave to drain on kitchen paper.
Spoon 2 tbsp of the oil from frying the shallots into a large wok and get it smoking hot. Add 2 tbsp of the nasi goreng paste and stir-fry for 2 minutes.
Add the cooked rice and stir-fry over a high heat for another 2 minutes, until it has heated through.
Add the prawns, the strips of omelette, the fried shallots and the flaked mackerel and stir-fry for another minute.
Add the soy sauce, cucumber and most of the spring onions, toss together well and then spoon on to a large warmed plate. Sprinkle with the remaining spring onions and serve straight away.