Prepare the ingredients.
Slice the red onion thinly. Set aside.
Remove the stems and dark spots from the eggplants. Cut them into half length-wise, and chop them into semi-circles.
Heat the cooking oil in a non-stick pan over medium heat.
Fry the sliced onions in the pan once the oil is hot, for about 1 minute or until fragrant.
Add the sambal paste to the pan. Stir fry constantly to prevent splatters, for about 2 minutes, or until the onions are soft and translucent.
Next, drain the water from the eggplants. Add the eggplants to the pan and stir evenly.
Stir in 75 ml of water if it looks dry. Cover the pan and let it braise for 10 minutes, rotating the sambal every 2-3 minutes to prevent burning at the bottom of the pan.
After 10 minutes, open the cover and stir in another 75 ml of water if it is dry.
Add the sardine, fish sauce and sugar. Stir until all the ingredients are well combined. Optionally, break the sardine into smaller chunks as you stir. Cover and let it cook for 3 minutes.
Check the softness of the eggplants. Taste and adjust as preferred.
Add the stems of the spring onions, stirring to soften them.
Switch off the heat.
Transfer to the serving bowl and top with the spring onion leaves. Serve with rice.