- Step 1
To make the mash, steam the potato and carrot in a steaming basket over a saucepan of simmering water for 8-10 minutes or until tender. Transfer to a heatproof bowl. Add ginger, milk and butter, and use a potato masher to mash until smooth. Taste and season with salt.
- Step 2
Meanwhile, heat the oil in a medium saucepan over medium heat. Add garlic, chilli, cumin and coriander and cook, stirring, for 30 seconds or until fragrant. Reduce heat to low. Add the wine and bring to a simmer. Simmer, uncovered, stirring occasionally, for 2 minutes. Add the butter, 1 cube at a time, whisking constantly and adding another cube only when the previous cube has been completely incorporated. Remove from heat. Stir in the grapefruit juice. Taste and season with salt and pepper.
- Step 3
Preheat a barbecue grill or chargrill on high. Add fish and cook for 2 minutes each side or until cooked through.
- Step 4
Spoon the mash among serving plates. Top with fish and rocket leaves. Drizzle with sauce and serve immediately.