Add the ingredients for the spice paste into a food processor and blend until you get a smooth paste. Alternatively, you can use a mortar and pestle if preferred.
For the sambal chilli sauce:
Heat up the non-stick frying pan with 3 tablespoons of extra virgin olive oil on medium to high heat. Pan fry the garlic, shallots, onion and ginger on low to medium heat until the garlic are lightly golden and onion are caramelised.
Then add in the spice paste, curry leaves, tamarind paste or puree, sugar and salt and pan fry for 3 minutes on medium heat until the spice paste is aromatic. Add in the water and stir-fry for another 2 minutes. Turn off the heat, remove and set aside in a bowl. Clean wok with kitchen paper towel.
For cooking the mackerel:
Marinade the mackerel cutlets with the marinade prepared. Rub and mix well into the mackerel cutlets.
Lightly coat the mackerel cutlets with corn starch, shake off excess.
Heat up a non-stick frying pan with some rice bran oil and pan fry the mackerel cutlets for 3 minutes on each side or until mackerel are golden brown. Pan fry in 3 to 4 batches, adding more rice bran oil as needed.
Pre-heat fan forced oven to 160C or 320F. Place the mackerel cutlets in a baking tray lined with baking paper. Bake the mackerel cutlets for 3 to 5 minutes or until the mackerel pieces are well browned.
Serve with sambal chilli sauce and steamed basmati rice.