Heat the oven to 200°C / 180°C fan. Cut the potatoes into roughly 2 cm pieces so they cook evenly.

Melt the butter gently and stir in the crushed garlic. Toss the potatoes through the garlic butter, spread over a roasting tray and add a little of the salt and pepper. Roast for about 45–50 minutes, turning halfway, until tender inside and golden outside.

Meanwhile, peel the carrots, then use the peeler to make thin ribbons. Wash the leek well and cut into fine strips. Peel and finely slice the small onion.

Lay out one generous piece of foil per person on a baking tray. Divide the vegetables between them, place a basa fillet on top of each, and add the thyme and a little more of the salt and pepper. Fold up the foil edges, divide the wine equally between the parcels, then seal loosely with room for steam.

When the potatoes have had about 20 minutes, put the fish parcels in the oven alongside them. Bake for about 25–30 minutes; the thickness of the fillets and your oven will affect the time. The fish must be hot all the way through, with opaque flesh that separates easily with a fork. If using a clean food thermometer, check that the centre reaches 75°C for at least 30 seconds.

Open the parcels carefully, directing the hot steam away from your face and hands. Serve the fish, vegetables and cooking juices with the garlic potatoes. Finish the potatoes with the remaining flaky salt, to taste.