Step 1

To make this dish you will need a well-chilled blender bowl and mixing bowl to make the fish mousse, so place them in the fridge or freezer a good few hours before you begin. Having all the ingredients for the fish mousse chilled is important as it keeps the mousse stable and tightens the protein, allowing you to incorporate all the cream

Step 2

Make a brine for the turbot. Bring the water, salt and sugar to the boil in a pan until completely dissolved, then set aside to cool completely

Step 3

While the brine is cooling, make the fish mousse. Blend the fish trim in the chilled blender bowl with a good pinch of salt until smooth. Add the egg white and blend again until smooth, then add the single cream and blend once more. Pass through a very fine sieve into the chilled bowl, then beat in the double cream gradually until smooth

Step 4

Wrap a small amount of the mousse in cling film and poach for a few minutes in a pan of simmering water to check for seasoning. Add more salt (if needed) to the rest of the mousse, then set aside in the fridge

Step 5

For the sauce, place the butter in a saucepan and heat until foaming. Add the shallots and cook for 5 minutes until soft, then add the mussels (discard any that are already open) with the white wine and turn the heat up to high. Cover and allow to steam for 2–3 minutes, or until the mussels open (discard any that remain closed). Strain and reserve the liquid, then pick the meat from the mussels. Weigh out 75g of cooked mussel meat, chop it up and stir into the mousse

Step 6

When the brine has cooled completely, place the turbot portions into it so they’re completely submerged and leave for 5 minutes. Remove and rinse in cold water, then pat dry. Top each piece of turbot with 60g of the mousse, then wrap tightly in cling film to form a pillow shape. Set aside in the fridge until ready to cook

Step 7

Bring a pan of salted water to the boil and add the potatoes. Cook for 9 minutes then add the asparagus and cook both for 1 more minute or until tender. Drain and refresh the asparagus in iced water, and when the potatoes are cool enough to handle, peel. Set aside to reheat later

Step 8

Make a dulse butter by blending the butter and dulse flakes together, then set aside in the fridge

Step 9

Reduce the reserved mussel liquor by two-thirds, then add the double cream and reduce by a third. Start to whisk 50g of the dulse butter into the sauce bit by bit until it thickly coats the back of a spoon. If the sauce looks like it’s about to split, add a splash of cold water. If it splits completely, it can be recovered by reducing a little cream by half and then whisking the split sauce into this. Finish the sauce with the chopped parsley and a few drops of lemon juice. Keep warm

Step 10

When ready to serve, set up a steamer and cook the turbot fillets at 60°C until their internal temperature reaches 50°C (about 15 minutes). If you don’t have a precise steamer then you can use a bamboo one set over a pan of simmering water; just be sure to keep an eye on the internal temperature. You could also use sous vide if you wish

Step 11

Meanwhile, warm the potatoes and asparagus in a little water with 50g of the dulse butter. Drop in the sea purslane right before serving to just warm through

Step 12

To serve, unwrap the fish and place on the plate. Glaze with the sauce, ensuring it is completely covered. Finish with the potatoes, asparagus and sea purslane, garnish with the fennel herb and serve with extra sauce on the side