We love blue-eye trevalla for its soft, creamy texture that holds together in the pan. Here, we've luxed it up in a gently spiced butter and served it atop a veg-heavy biryani for light-leaning bowls that pretty much demand everyone gives you a pat on the back.
Boil kettle. Peel and finely slice onion into half-moons. Grate carrot on the coarse side of a box grater. Dissolve stock cube in 310ml (1¼ cups) boiling water.
Heat ½ the olive oil in a deep frypan over medium-high heat. Add onion with ¼ teaspoon salt flakes and cook, stirring occasionally, for 4–5 minutes or until starting to caramelise. Stir through cumin seeds and carrot for 30 seconds or until fragrant.
Add rice and stock to saucepan and increase heat to high. Bring to a boil, cover with a lid and reduce heat to low. Cook for 15–17 minutes or until rice is cooked through. Remove from heat, add spinach and cover with a lid. Set aside for 5 minutes.
Zest lime. Place lime zest, korma paste and butter in a bowl and mash with a fork to combine.
Heat remaining oil in a frypan over medium-high heat. Season fish with salt and cook, skin-side down, for 4 minutes. Turn and cook for a further 4 minutes or until fish is cooked through. Add korma butter to pan and cook for 30 seconds to coat fish in butter.
Roughly chop cashews. Slice lime into wedges. Divide biryani between bowls and top with fish and cashews. Serve with yoghurt on the side.