Preheat the oven to 180°C / 160°C (fan oven) / 360°F / Gas Mark 4. Put the potatoes in a large pan and cover with cold wter. Bring to the boil, then simmer for 15 minutes until just tender. Drain and set aside to cool slightly.

Meanwhile, steam the leeks in a steamer set over the pan of simmering potatoes for 3-4 minutes or until just tender. Set aside.

Cut decent sized rectangles from baking paper. Carefully lay a halibut fillet on one half of each paper rectangle. Scatter over half the dill, top with the lemon slices and season well with salt and freshly ground black pepper. Fold the other half of each paper over the fish and pleat the edges to seal. Put in a roasting tin and bake for 10-12 minutes or until the fish is cooked through and juicy.

While the fish is cooking, halve the cooked new potatoes lengthways. Heat a nonstick frying pan over a medium heat and mist with cooking spray. Add the potatoes and leeks, season well, and fry until golden.

Mix the yogurt with the lemon juice and remaining dill, season to taste. Serve with fish and veg.