Put the kettle on. Then, with a pair of scissors, snip the chillies into 2-3 pieces straight into a medium bowl.
20 dried red chillies
Pour the boiling water over the chillies, cover, and leaves to soak for 15 minutes. Get the other ingredients ready while waiting.
250 ml water
Other Prep Work
Peel and halve the onion. Then thinly slice half of the onion and set aside. Cut the other half in two and drop into the chopper.
1 large onion
Peel the garlic and drop into the chopper. Add the shrimp paste.
2 medium cloves garlic, 1 tsp shrimp paste
When the chillies are done soaking, drain and rinse them, then tip them into the chopper. Chop everything into a fairly fine paste. Add a little water if you need it, but it shouldn't really be necessary.
Let's get Cooking
Heat the oil in a medium-sized wok or frying pan, over medium heat. Sauté the sliced onions for 1 minute.
2 Tbsp vegetable oil
Then tip in the ground ingredients and fry this chilli paste for 2 minutes.
Pour the water into your chopper (to "rinse" it), then pour the whole lot into the wok. Add the salt and sugar and stir to mix. Bring to a simmer, then reduce the heat to low and cook for 20 minutes, until the sambal is reduced and has thickened.
250 ml water, 1 Tbsp white sugar, ½ tsp salt
Tip in the fish balls, bring the heat back up to medium and stir well. Reduce the heat to medium-low and cook for 5 minutes until the fishballs are done.
500 g fish balls
Check seasoning, and add more salt if it needs it. Take it off the heat.
Stir in the lime juice, leave to rest for 2 minutes, then serve.Will keep overnight, covered, in the fridge. See notes below about making ahead.
1 Tbsp fresh lime juice
Notes
To Make AheadMake the sambal sauce itself up to 2 days ahead (without the fishballs), and store in the fridge. Add the fishballs before serving, heating up the sambal, and cooking the fishballs through.