Step 1

For spice paste, drain chillies then blend with shallots and candlenuts in a food processor to a fine paste, adding a little water to loosen if required.

Step 2

Combine fish with turmeric, chilli powder and 1 tsp salt in a large bowl, turn to coat and set aside to marinate (15 minutes).

Step 3

Heat a wok or frying pan with 60ml oil over medium-high heat. When oil begins to shimmer, add fish, skin-side down, and cook, turning once, until skin is crisp and fish is cooked through (2-3 minutes each side; be careful, hot oil will spit). Drain on paper towels.

Step 4

Wipe out wok with paper towels, return to medium heat and add remaining oil. When hot, add spice paste, and stir until fragrant and oil separates (8-10 minutes). Add vinegar, sugar, soy sauce and 250ml water, bring to the boil, then reduce heat to medium and simmer until sambal sauce is slightly thickened (2-3 minutes). Add fish and stir gently to warm through. Season to taste and serve scattered with spring onion.