Preheat your oven to 220°C/200°C fan/gas mark 7. Chop the potato and sweet potato into 2cm chunks (no need to peel). Pop them onto a large baking tray. Drizzle with oil, season with salt and pepper then toss to coat. Spread out in a single layer. TIP: Use two baking trays if necessary.
When the oven is hot, roast on the top shelf until golden, 25-30 mins. Turn halfway through.

Peel and grate the garlic (or use a garlic press).
Zest and halve the lemon. Finely chop the chives (use scissors if easier). TIP: Discard any tough stalks from the cavolo nero at this stage.

Drizzle the sea bass with the olive oil for the marinade (see ingredients for amount).
Season with salt and half the Cajun spice mix. Rub this onto both sides of the fish. IMPORTANT: Wash your hands and equipment after handling raw fish.
In a small bowl, mix the remaining Cajun spice mix with half the chives, a pinch of lemon zest, a squeeze of lemon juice and the olive oil for the dressing (see ingredients for amount). Season with salt and set the chive dressing to one side.

Heat a drizzle of oil in a large frying pan on high heat. Add the cavolo nero and a splash of water and cover until wilted, 3-4 mins.
Remove the lid, add the garlic and stir-fry for 1 min more.
Season to taste with salt and pepper. Transfer to a large bowl and cover to keep warm.

Wipe out your (now empty) frying pan and pop on medium-high heat (no oil).
Once hot, carefully place your sea bass into the pan, skin-side down.
Cook for 3-4 mins before turning over and cooking for 2-3 mins on the other side. TIP: To get crispy skin on the fish, don't move it around when it's cooking skin-side down. IMPORTANT: The fish is cooked when opaque in the middle.

When the potatoes are cooked, add them to your bowl of cavolo nero and roughly mash. Mix in a knob of butter (if you have any) and the remaining chives. Season to taste with salt and pepper.
Serve your mash topped with the Cajun spiced sea bass and a drizzle of chive dressing.
Chop any remaining lemon into wedges and serve alongside for squeezing over. Enjoy!