Place onion, garlic and candlenuts or macadamias in a large mortar and pound with a pestle until a thick coarse paste forms. (Alternatively, place in a food processor and process until a coarse paste forms.)
Heat oil in a large deep-frying pan or saucepan on high until smoking. Reduce heat to medium. Add paste and cook, stirring, for 8-10 minutes or until oil splits from paste. Stir in chilli powder, aniseed, turmeric and cumin. Cook, stirring, until fragrant and caramelised, being careful not to let the paste burn.
Add water and bring to the boil. Stir in tamarind puree and pineapple. Simmer for 3-5 minutes or until pineapple softens. Add fish, salt, sugar and fish sauce. Bring to the boil on high, then reduce heat to low. Cook, covered, for 5 minutes or until sauce just thickens. Set aside, covered, for a further 5 minutes or until fish is cooked through and flakes easily when gently pressed. Taste and adjust seasoning with sugar, salt and tamarind as needed.
To serve, garnish curry with mint and serve with steamed rice and lime wedges.
