1: Heat the olive oil in a large saucepan over a medium heat. Add the garlic and onion and fry, stirring occasionally, for at least 5 minutes until softened, but not coloured. Add the mushrooms and fry for a further 2–3 minutes until they are just softened.
2: Stir in the wild rice, then add the vegetable stock and bring to the boil. Reduce the heat to medium, cover the pan and leave to simmer for about 45 minutes until the rice is tender and all the stock has been absorbed.
3: Remove the pan from the heat, stir in the lemon zest and season. Leave the wild rice mix to cool completely. When it’s cool, add the mozzarella and dill and gently stir them though the wild rice, then leave to one side until needed.
4: Meanwhile, bring a saucepan of salted water to the boil and place a bowl of iced water in the sink. Put the spinach and the sorrel into the boiling water and blanch for about 2 seconds to just soften. Drain them well, then immediately plunge them into the iced water to stop the cooking and set the colour. Drain again. Lay the spinach and sorrel leaves out on a dry clean tea towel to soak up any water.
5: Place a large sheet of clingfilm over your work surface and arrange a layer of the dry spinach and sorrel on top, then season. Put a large spoonful or two of the rice mix on top of the spinach, then place the fish on top of the rice. Cover the fish with the remaining rice mix, then wrap over the remaining spinach and sorrel. You are looking for a green parcel. Wrap this parcel in the clingfilm tightly and leave to rest for 1–2 hours in the fridge.
6: After the halibut has rested, roll out the puff pastry on a lightly floured surface into a rectangle ½ cm thick. Cut out the corners to make it look like a cross. Remove the clingfilm from the halibut parcel and place the parcel in the centre of the cross. Wrap the fish up in the puff pastry and use the egg glaze to seal the edges. Place it seam-side down on a piece of baking parchment on a thick baking sheet and place in the fridge for at least 1 hour or up to 2 hours.
7: Meanwhile, make the lime cream. Pour the double cream into a bowl. Grate the zest of the lime on top and then squeeze the juice through a fine sieve into the cream. Whisk until the cream thickens. Add the cracked black pepper and a pinch of salt. Cover and chill until needed.
8: When you are ready to bake, preheat the oven to 200°C/Gas Mark 6 and glaze the pastry with the egg wash. Put the baking sheet in the oven and roast the halibut parcel for 25–30 minutes until the pastry is golden brown. Remove from the oven and leave the parcel to rest for 5–10 minutes before slicing. Serve with the lime cream.